Econstudentlog

A few diabetes papers of interest

A couple of weeks ago I decided to cover some of the diabetes articles I’d looked at and bookmarked in the past, but there were a lot of articles and I did not get very far. This post will cover some more of these articles I had failed to cover here despite intending to do so at some point. Considering that I these days relatively regularly peruse e.g. the Diabetes Care archives I am thinking of making this sort of post a semi-regular feature of the blog.

i. Association Between Diabetes and Hippocampal Atrophy in Elderly Japanese: The Hisayama Study.

“A total of 1,238 community-dwelling Japanese subjects aged ≥65 years underwent brain MRI scans and a comprehensive health examination in 2012. Total brain volume (TBV), intracranial volume (ICV), and hippocampal volume (HV) were measured using MRI scans for each subject. We examined the associations between diabetes-related parameters and the ratios of TBV to ICV (an indicator of global brain atrophy), HV to ICV (an indicator of hippocampal atrophy), and HV to TBV (an indicator of hippocampal atrophy beyond global brain atrophy) after adjustment for other potential confounders.”

“The multivariable-adjusted mean values of the TBV-to-ICV, HV-to-ICV, and HV-to-TBV ratios were significantly lower in the subjects with diabetes compared with those without diabetes (77.6% vs. 78.2% for the TBV-to-ICV ratio, 0.513% vs. 0.529% for the HV-to-ICV ratio, and 0.660% vs. 0.676% for the HV-to-TBV ratio; all P < 0.01). These three ratios decreased significantly with elevated 2-h postload glucose (PG) levels […] Longer duration of diabetes was significantly associated with lower TBV-to-ICV, HV-to-ICV, and HV-to-TBV ratios. […] Our data suggest that a longer duration of diabetes and elevated 2-h PG levels, a marker of postprandial hyperglycemia, are risk factors for brain atrophy, particularly hippocampal atrophy.”

“Intriguingly, our findings showed that the subjects with diabetes had significantly lower mean HV-to-TBV ratio values, indicating […] that the hippocampus is predominantly affected by diabetes. In addition, in our subjects a longer duration and a midlife onset of diabetes were significantly associated with a lower HV, possibly suggesting that a long exposure of diabetes particularly worsens hippocampal atrophy.”

The reason why hippocampal atrophy is a variable of interest to these researchers is that hippocampal atrophy is a feature of Alzheimer’s Disease, and diabetics have an elevated risk of AD. This is incidentally far from the first study providing some evidence for the existence of potential causal linkage between impaired glucose homeostasis and AD (see e.g. also this paper, which I’ve previously covered here on the blog).

ii. A Population-Based Study of All-Cause Mortality and Cardiovascular Disease in Association With Prior History of Hypoglycemia Among Patients With Type 1 Diabetes.

“Although patients with T1DM may suffer more frequently from hypoglycemia than those with T2DM (8), very few studies have investigated whether hypoglycemia may also increase the risk of CVD (6,9,10) or death (1,6,7) in patients with T1DM; moreover, the results of these studies have been inconclusive (6,9,10) because of the dissimilarities in their methodological aspects, including their enrollment of populations with T1DM with different levels of glycemic control, application of different data collection methods, and adoption of different lengths of observational periods.”

“Only a few population-based studies have examined the potential cumulative effect of repeated severe hypoglycemia on all-cause mortality or CVD incidence in T1DM (9). The Action to Control Cardiovascular Risk in Diabetes (ACCORD) study of T2DM found a weakly inverse association between the annualized number of hypoglycemic episodes and the risk of death (11,12). By contrast, some studies find that repeated hypoglycemia may be an aggravating factor to atherosclerosis in T1DM (13,14). Studies on the compromised sympathetic-adrenal reaction in patients with repeated hypoglycemia have been inconclusive regarding whether such a reaction may further damage intravascular coagulation and thrombosis (15) or decrease the vulnerability of these patients to adverse health outcomes (12).

Apart from the lack of information on the potential dose–gradient effect associated with severe hypoglycemic events in T1DM from population-based studies, the risks of all-cause mortality/CVD incidence associated with severe hypoglycemia occurring at different periods before all-cause mortality/CVD incidence have never been examined. In this study, we used the population-based medical claims of a cohort of patients with T1DM to examine whether the risks of all-cause mortality/CVD incidence are associated with previous episodes of severe hypoglycemia in different periods and whether severe hypoglycemia may pose a dose–gradient effect on the risks of all-cause mortality/CVD incidence.”

“Two nested case-control studies with age- and sex-matched control subjects and using the time-density sampling method were performed separately within a cohort of 10,411 patients with T1DM in Taiwan. The study enrolled 564 nonsurvivors and 1,615 control subjects as well as 743 CVD case subjects and 1,439 control subjects between 1997 and 2011. History of severe hypoglycemia was identified during 1 year, 1–3 years, and 3–5 years before the occurrence of the study outcomes.”

“Prior severe hypoglycemic events within 1 year were associated with higher risks of all-cause mortality and CVD (adjusted OR 2.74 [95% CI 1.96–3.85] and 2.02 [1.35–3.01], respectively). Events occurring within 1–3 years and 3–5 years before death were also associated with adjusted ORs of 1.94 (95% CI 1.39–2.71) and 1.68 (1.15–2.44), respectively. Significant dose–gradient effects of severe hypoglycemia frequency on mortality and CVD were observed within 5 years. […] we found that a greater frequency of severe hypoglycemia occurring 1 year before death was significantly associated with a higher OR of all-cause mortality (1 vs. 0: 2.45 [95% CI 1.65–3.63]; ≥2 vs. 0: 3.49 [2.01–6.08], P < 0.001 for trend). Although the strength of the association was attenuated, a significant dose–gradient effect still existed for severe hypoglycemia occurring in 1–3 years (P < 0.001 for trend) and 3–5 years (P < 0.015 for trend) before death. […] Exposure to repeated severe hypoglycemic events can lead to higher risks of mortality and CVD.”

“Our findings are supported by two previous studies that investigated atherosclerosis risk in T1DM (13,14). The DCCT/EDIC project reported that the prevalence of coronary artery calcification, an established atherosclerosis marker, was linearly correlated with the incidence rate of hypoglycemia on the DCCT stage (14). Giménez et al. (13) also demonstrated that repeated episodes of hypoglycemia were an aggravating factor for preclinical atherosclerosis in T1DM. […] The mechanism of hypoglycemia that predisposes to all-cause mortality/CVD incidence remains unclear.”

iii. Global Estimates on the Number of People Blind or Visually Impaired by Diabetic Retinopathy: A Meta-analysis From 1990 to 2010.

“On the basis of previous large-scale population-based studies and meta-analyses, diabetic retinopathy (DR) has been recognized as one of the most common and important causes for visual impairment and blindness (1–19). These studies in general showed that DR was the leading cause of blindness globally among working-aged adults and therefore has a significant socioeconomic impact (20–22).”

“A previous meta-analysis (21) summarizing 35 studies with more than 20,000 patients with diabetes estimated a prevalence of any DR of 34.6%, of diabetic macular edema of 6.8%, and of vision-threating DR of 10.2% within the diabetes population. […] Yau et al. (21) estimated that ∼93 million people had some DR and 28 million people had sight-threatening stages of DR. However, this meta-analysis did not address the prevalence of visual impairment and blindness due to DR and thus the impact of DR on the general population. […] We therefore conducted the present meta-analysis of all available population-based studies performed worldwide within the last two decades as part of the Global Burden of Disease Study 2010 (GBD) to estimate the number of people affected by blindness and visual impairment.”

“DR [Diabetic Retinopathy] ranks as the fifth most common cause of global blindness and of global MSVI [moderate and severe vision impairment] (25). […] this analysis estimates that, in 2010, 1 out of every 39 blind people had blindness due to DR and 1 out of every 52 people had visual impairment due to DR. […] Globally in 2010, out of overall 32.4 million blind and 191 million visually impaired people, 0.8 million were blind and 3.7 million were visually impaired because of DR, with an alarming increase of 27% and 64%, respectively, spanning the two decades from 1990 to 2010. DR accounted for 2.6% of all blindness in 2010 and 1.9% of all MSVI worldwide, increasing from 2.1% and 1.3%, respectively, in 1990. […] The number of persons with visual impairment due to DR worldwide is rising and represents an increasing proportion of all blindness/MSVI causes. Age-standardized prevalence of DR-related blindness/MSVI was higher in sub-Saharan Africa and South Asia.”

“Our data suggest that the percentage of blindness and MSVI attributable to DR was lower in low-income regions with younger populations than in high-income regions with older populations. There are several reasons that may explain this observation. First, low-income societies may have a higher percentage of unoperated cataract or undercorrected refractive error–related blindness and MSVI (25), which is probably related to access to visual and ocular health services. Therefore, the proportional increase in blindness and MSVI attributable to DR may be rising because of the decreasing proportion attributable to cataract (25) as a result of the increasing availability of cataract surgery in many parts of the world (29) during the past decade. Improved visualization of the fundus afforded by cataract surgery should also improve the detection of DR. The increase in the percentage of global blindness caused by DR within the last two decades took place in all world regions except Western Europe and high-income North America where there was a slight decrease. This decrease may reflect the effect of intensified prevention and treatment of DR possibly in part due to the introduction of intravitreal injections of steroids and anti-VEGF (vascular endothelial growth factor) drugs (30,31).

Second, in regions with poor medical infrastructure, patients with diabetes may not live long enough to experience DR (32). This reduces the number of patients with diabetes, and, furthermore, it reduces the number of patients with DR-related vision loss. Studies in the literature have reported that the prevalence of severe DR decreased from 1990 to 2010 (21) while the prevalence of diabetes simultaneously increased (27), which implies a reduction in the prevalence of severe DR per person with diabetes. […] Third, […] younger populations may have a lower prevalence of diabetes (33). […] Therefore, considering further economic development in rural regions, improvements in medical infrastructure, the general global demographic transition to elderly populations, and the association between increasing economic development and obesity, we project the increase in the proportion of DR-related blindness and MSVI to continue to rise in the future.”

iv. Do Patient Characteristics Impact Decisions by Clinicians on Hemoglobin A1c Targets?

“In setting hemoglobin A1c (HbA1c) targets, physicians must consider individualized risks and benefits of tight glycemic control (1,2) by recognizing that the risk-benefit ratio may become unfavorable in certain patients, including the elderly and/or those with multiple comorbidities (3,4). Customization of treatment goals based on patient characteristics is poorly understood, partly due to insufficient data on physicians’ decisions in setting targets. We used the National Health and Nutrition Examination Survey (NHANES) to analyze patient-reported HbA1c targets set by physicians and to test whether targets are correlated with patient characteristics.”

“we did not find any evidence that U.S. physicians systematically consider important patient-specific information when selecting the intensity of glycemic control. […] the lack of variation with patient characteristics suggests overreliance on a general approach, without consideration of individual variation in the risks and benefits (or patient preference) of tight control.”

v. Cardiovascular Autonomic Neuropathy, Sexual Dysfunction, and Urinary Incontinence in Women With Type 1 Diabetes.

“This study evaluated associations among cardiovascular autonomic neuropathy (CAN), female sexual dysfunction (FSD), and urinary incontinence (UI) in women with type I diabetes mellitus (T1DM). […] We studied 580 women with T1DM in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study (DCCT/EDIC).”

“At EDIC year 17, FSD was observed in 41% of women and UI in 30%. […] We found that CAN was significantly more prevalent among women with FSD and/or UI, because 41% of women with FSD and 44% with UI had positive measures of CAN compared with 30% without FSD and 38% without UI at EDIC year 16/17. We also observed bivariate associations between FSD and several measures of CAN […] In long-standing T1DM, CAN may predict development of FSD and may be a useful surrogate for generalized diabetic autonomic neuropathy.”

“Although autonomic dysfunction has been considered an important factor in the etiology of many diabetic complications, including constipation, exercise intolerance, bladder dysfunction, erectile dysfunction, orthostatic hypotension, and impaired neurovascular function, our study is among the first to systematically demonstrate a link between CAN and FSD in a large cohort of well-characterized patients with T1DM (14).”

vi. Correlates of Medication Adherence in the TODAY Cohort of Youth With Type 2 Diabetes.

“A total of 699 youth 10–17 years old with recent-onset type 2 diabetes and ≥80% adherence to metformin therapy for ≥8 weeks during a run-in period were randomized to receive one of three treatments. Participants took two study pills twice daily. Adherence was calculated by pill count from blister packs returned at visits. High adherence was defined as taking ≥80% of medication; low adherence was defined as taking <80% of medication.”

“In this low socioeconomic cohort, high and low adherence did not differ by sex, age, family income, parental education, or treatment group. Adherence declined over time (72% high adherence at 2 months, 56% adherence at 48 months, P < 0.0001). A greater percentage of participants with low adherence had clinically significant depressive symptoms at baseline (18% vs. 12%, P = 0.0415). No adherence threshold predicted the loss of glycemic control. […] Most pediatric type 1 diabetes studies (5–7) consistently document a correlation between adherence and race, ethnicity, and socioeconomic status, and studies of adults with type 2 diabetes (8,9) have documented that depressed patients are less adherent to their diabetes regimen. There is a dearth of information in the literature regarding adherence to medication in pediatric patients with type 2 diabetes.”

“In the cohort, the presence of baseline clinically significant depressive symptoms was associated with subsequent lower adherence. […] The TODAY cohort demonstrated deterioration in study medication adherence over time, irrespective of treatment group assignment. […] Contrary to expectation, demographic factors (sex, race-ethnicity, household income, and parental educational level) did not predict medication adherence. The lack of correlation with these factors in the TODAY trial may be explained by the limited income and educational range of the families in the TODAY trial. Nearly half of the families in the TODAY trial had an annual income of <$25,000, and, for over half of the families, the highest level of parental education was a high school degree or lower. In addition, our run-in criteria selected for more adherent subjects. All subjects had to have >80% adherence to M therapy for ≥8 weeks before they could be randomized. This may have limited variability in medication adherence postrandomization. It is also possible that selecting for more adherent subjects in the run-in period also selected for subjects with a lower frequency of depressive symptoms.”

“In the TODAY trial, baseline clinically significant depressive symptoms were more prevalent in the lower-adherence group, suggesting that regular screening for depressive symptoms should be undertaken to identify youth who were at high risk for poor medication adherence. […] Studies in adults with type 2 diabetes (2328) consistently report that depressed patients are less adherent to their diabetes regimen and experience more physical complications of diabetes. Identifying youth who are at risk for poor medication adherence early in the course of disease would make it possible to provide support and, if needed, specific treatment. Although we were not able to determine whether the treatment of depressive symptoms changed adherence over time, our findings support the current guidelines for psychosocial screening in youth with diabetes (29,30).”

vii. Increased Risk of Incident Chronic Kidney Disease, Cardiovascular Disease, and Mortality in Patients With Diabetes With Comorbid Depression.

Another depression-related paper, telling another part of the story. If depressed diabetics are less compliant/adherent, which seems – as per the above study – to be the case both in the context of the adult and pediatric patient population, then you might also expect this reduced compliance/adherence to ‘translate’ into this group having poorer metabolic control, and thus be at higher risk of developing microvascular complications such as nephropathy. This seems to be what we observe, at least according to the findings of this study:

“It is not known if patients with diabetes with depression have an increased risk of chronic kidney disease (CKD). We examined the association between depression and incident CKD, mortality, and incident cardiovascular events in U.S. veterans with diabetes.”

“Among a nationally representative prospective cohort of >3 million U.S. veterans with baseline estimated glomerular filtration rate (eGFR) ≥60 mL/min/1.73 m2, we identified 933,211 patients with diabetes. Diabetes was ascertained by an ICD-9-CM code for diabetes, an HbA1c >6.4%, or receiving antidiabetes medication during the inclusion period. Depression was defined by an ICD-9-CM code for depression or by antidepressant use during the inclusion period. Incident CKD was defined as two eGFR levels 2 separated by ≥90 days and a >25% decline in baseline eGFR.”

“Depression was associated with 20% higher risk of incident CKD (adjusted hazard ratio [aHR] and 95% CI: 1.20 [1.19–1.21]). Similarly, depression was associated with increased all-cause mortality (aHR and 95% CI: 1.25 [1.24–1.26]). […] The presence of depression in patients with diabetes is associated with higher risk of developing CKD compared with nondepressed patients.”

It’s important to remember that the higher reported eGFRs in the depressed patient group may not be important/significant, and they should not be taken as an indication of relatively better kidney function in this patient population – especially in the type 2 context, the relationship between eGFR and kidney function is complicated. I refer to Bakris et al.‘s text on these topics for details (blog coverage here).

May 6, 2017 Posted by | Cardiology, Diabetes, Medicine, Nephrology, Neurology, Psychology, Studies | Leave a comment

A few diabetes papers of interest

1. Cognitive Dysfunction in Older Adults With Diabetes: What a Clinician Needs to Know. I’ve talked about these topics before here on the blog (see e.g. these posts on related topics), but this is a good summary article. I have added some observations from the paper below:

“Although cognitive dysfunction is associated with both type 1 and type 2 diabetes, there are several distinct differences observed in the domains of cognition affected in patients with these two types. Patients with type 1 diabetes are more likely to have diminished mental flexibility and slowing of mental speed, whereas learning and memory are largely not affected (8). Patients with type 2 diabetes show decline in executive function, memory, learning, attention, and psychomotor efficiency (9,10).”

“So far, it seems that the risk of cognitive dysfunction in type 2 diabetes may be influenced by glycemic control, hypoglycemia, inflammation, depression, and macro- and microvascular pathology (14). The cumulative impact of these conditions on the vascular etiology may further decrease the threshold at which cognition is affected by other neurological conditions in the aging brain. In patients with type 1 diabetes, it seems as though diabetes has a lesser impact on cognitive dysfunction than those patients with type 2 diabetes. […] Thus, the cognitive decline in patients with type 1 diabetes may be mild and may not interfere with their functionality until later years, when other aging-related factors become important. […] However, recent studies have shown a higher prevalence of cognitive dysfunction in older patients (>60 years of age) with type 1 diabetes (5).”

“Unlike other chronic diseases, diabetes self-care involves many behaviors that require various degrees of cognitive pliability and insight to perform proper self-care coordination and planning. Glucose monitoring, medications and/or insulin injections, pattern management, and diet and exercise timing require participation from different domains of cognitive function. In addition, the recognition, treatment, and prevention of hypoglycemia, which are critical for the older population, also depend in large part on having intact cognition.

The reason a clinician needs to recognize different domains of cognition affected in patients with diabetes is to understand which self-care behavior will be affected in that individual. […] For example, a patient with memory problems may forget to take insulin doses, forget to take medications/insulin on time, or forget to eat on time. […] Cognitively impaired patients using insulin are more likely to not know what to do in the event of low blood glucose or how to manage medication on sick days (34). Patients with diminished mental flexibility and processing speed may do well with a simple regimen but may fail if the regimen is too complex. In general, older patients with diabetes with cognitive dysfunction are less likely to be involved in diabetes self-care and glucose monitoring compared with age-matched control subjects (35). […] Other comorbidities associated with aging and diabetes also add to the burden of cognitive impairment and its impact on self-care abilities. For example, depression is associated with a greater decline in cognitive function in patients with type 2 diabetes (36). Depression also can independently negatively impact the motivation to practice self-care.”

“Recently, there is an increasing discomfort with the use of A1C as a sole parameter to define glycemic goals in the older population. Studies have shown that A1C values in the older population may not reflect the same estimated mean glucose as in the younger population. Possible reasons for this discrepancy are the commonly present comorbidities that impact red cell life span (e.g., anemia, uremia, renal dysfunction, blood transfusion, erythropoietin therapy) (45,46). In addition, A1C level does not reflect glucose excursions and variability. […] Thus, it is prudent to avoid A1C as the sole measure of glycemic goal in this population. […] In patients who need insulin therapy, simplification, also known as de-intensification of the regimen, is generally recommended in all frail patients, especially if they have cognitive dysfunction (37,49). However, the practice has not caught up with the recommendations as shown by large observational studies showing unnecessary intensive control in patients with diabetes and dementia (50–52).”

“With advances in the past few decades, we now see a larger number of patients with type 1 diabetes who are aging successfully and facing the new challenges that aging brings. […] Patients with type 1 diabetes are typically proactive in their disease management and highly disciplined. Cognitive dysfunction in these patients creates significant distress for the first time in their lives; they suddenly feel a “lack of control” over the disease they have managed for many decades. The addition of autonomic dysfunction, gastropathy, or neuropathy may result in wider glucose excursions. These patients are usually more afraid of hyperglycemia than hypoglycemia — both of which they have managed for many years. However, cognitive dysfunction in older adults with type 1 diabetes has been found to be associated with hypoglycemic unawareness and glucose variability (5), which in turn increases the risk of severe hypoglycemia (54). The need for goal changes to avoid hypoglycemia and accept some hyperglycemia can be very difficult for many of these patients.”

2. Trends in Drug Utilization, Glycemic Control, and Rates of Severe Hypoglycemia, 2006–2013.

“From 2006 to 2013, use increased for metformin (from 47.6 to 53.5%), dipeptidyl peptidase 4 inhibitors (0.5 to 14.9%), and insulin (17.1 to 23.0%) but declined for sulfonylureas (38.8 to 30.8%) and thiazolidinediones (28.5 to 5.6%; all P < 0.001). […] The overall rate of severe hypoglycemia remained the same (1.3 per 100 person-years; P = 0.72), declined modestly among the oldest patients (from 2.9 to 2.3; P < 0.001), and remained high among those with two or more comorbidities (3.2 to 3.5; P = 0.36). […] During the recent 8-year period, the use of glucose-lowering drugs has changed dramatically among patients with T2DM. […] The use of older classes of medications, such as sulfonylureas and thiazolidinediones, declined. During this time, glycemic control of T2DM did not improve in the overall population and remained poor among nearly a quarter of the youngest patients. Rates of severe hypoglycemia remained largely unchanged, with the oldest patients and those with multiple comorbidities at highest risk. These findings raise questions about the value of the observed shifts in drug utilization toward newer and costlier medications.”

“Our findings are consistent with a prior study of drug prescribing in U.S. ambulatory practice conducted from 1997 to 2012 (2). In that study, similar increases in DPP-4 inhibitor and insulin analog prescribing were observed; these changes were accompanied by a 61% increase in drug expenditures (2). Our study extends these findings to drug utilization and demonstrates that these increases occurred in all age and comorbidity subgroups. […] In contrast, metformin use increased only modestly between 2006 and 2013 and remained relatively low among older patients and those with two or more comorbidities. Although metformin is recommended as first-line therapy (26), it may be underutilized as the initial agent for the treatment of T2DM (27). Its use may be additionally limited by coexisting contraindications, such as chronic kidney disease (28).”

“The proportion of patients with a diagnosis of diabetes who did not fill any glucose-lowering medications declined slightly (25.7 to 24.1%; P < 0.001).”

That is, one in four people who had a diagnosis of type 2 diabetes were not taking any prescription drugs for their health condition. I wonder how many of those people have read wikipedia articles like this one

“When considering treatment complexity, the use of oral monotherapy increased slightly (from 24.3 to 26.4%) and the use of multiple (two or more) oral agents declined (from 33.0 to 26.5%), whereas the use of insulin alone and in combination with oral agents increased (from 6.0 to 8.5% and from 11.1 to 14.6%, respectively; all P values <0.001).”

“Between 1987 and 2011, per person medical spending attributable to diabetes doubled (4). More than half of the increase was due to prescription drug spending (4). Despite these spending increases and greater utilization of newly developed medications, we showed no concurrent improvements in overall glycemic control or the rates of severe hypoglycemia in our study. Although the use of newer and more expensive agents may have other important benefits (44), further studies are needed to define the value and cost-effectiveness of current treatment options.”

iii. Among Low-Income Respondents With Diabetes, High-Deductible Versus No-Deductible Insurance Sharply Reduces Medical Service Use.

“Using the 2011–2013 Medical Expenditure Panel Survey, bivariate and regression analyses were conducted to compare demographic characteristics, medical service use, diabetes care, and health status among privately insured adult respondents with diabetes, aged 18–64 years (N = 1,461) by lower (<200% of the federal poverty level) and higher (≥200% of the federal poverty level) income and deductible vs. no deductible (ND), low deductible ($1,000/$2,400) (LD), and high deductible (>$1,000/$2,400) (HD). The National Health Interview Survey 2012–2014 was used to analyze differences in medical debt and delayed/avoided needed care among adult respondents with diabetes (n = 4,058) by income. […] Compared with privately insured respondents with diabetes with ND, privately insured lower-income respondents with diabetes with an LD report significant decreases in service use for primary care, checkups, and specialty visits (27%, 39%, and 77% lower, respectively), and respondents with an HD decrease use by 42%, 65%, and 86%, respectively. Higher-income respondents with an LD report significant decreases in specialty (28%) and emergency department (37%) visits.”

“The reduction in ambulatory visits made by lower-income respondents with ND compared with lower-income respondents with an LD or HD is far greater than for higher-income patients. […] The substantial reduction in checkup (preventive) and specialty visits by those with a lower income who have an HDHP [high-deductible health plan, US] implies a very different pattern of service use compared with lower-income respondents who have ND and with higher-income respondents. Though preventive visits require no out-of-pocket costs, reduced preventive service use with HDHPs is well established and might be the result of patients being unaware of this benefit or their concern about findings that could lead to additional expenses (31). Such sharply reduced service use by low-income respondents with diabetes may not be desirable. Patients with diabetes benefit from assessment of diabetes control, encouragement and reinforcement of behavior change and medication use, and early detection and treatment of diabetes complications or concomitant disease.”

iv. Long-term Mortality and End-Stage Renal Disease in a Type 1 Diabetes Population Diagnosed at Age 15–29 Years in Norway.

OBJECTIVE To study long-term mortality, causes of death, and end-stage renal disease (ESRD) in people diagnosed with type 1 diabetes at age 15–29 years.

RESEARCH DESIGN AND METHODS This nationwide, population-based cohort with type 1 diabetes diagnosed during 1978–1982 (n = 719) was followed from diagnosis until death, emigration, or September 2013. Linkages to the Norwegian Cause of Death Registry and the Norwegian Renal Registry provided information on causes of death and whether ESRD was present.

RESULTS During 30 years’ follow-up, 4.6% of participants developed ESRD and 20.6% (n = 148; 106 men and 42 women) died. Cumulative mortality by years since diagnosis was 6.0% (95% CI 4.5–8.0) at 10 years, 12.2% (10.0–14.8) at 20 years, and 18.4% (15.8–21.5) at 30 years. The SMR [standardized mortality ratio] was 4.4 (95% CI 3.7–5.1). Mean time from diagnosis of diabetes to ESRD was 23.6 years (range 14.2–33.5). Death was caused by chronic complications (32.2%), acute complications (20.5%), violent death (19.9%), or any other cause (27.4%). Death was related to alcohol in 15% of cases. SMR for alcohol-related death was 6.8 (95% CI 4.5–10.3), for cardiovascular death was 7.3 (5.4–10.0), and for violent death was 3.6 (2.3–5.3).

CONCLUSIONS The cumulative incidence of ESRD was low in this cohort with type 1 diabetes followed for 30 years. Mortality was 4.4 times that of the general population, and more than 50% of all deaths were caused by acute or chronic complications. A relatively high proportion of deaths were related to alcohol.”

Some additional observations from the paper:

“Studies assessing causes of death in type 1 diabetes are most frequently conducted in individuals diagnosed during childhood (17) or without evaluating the effect of age at diagnosis (8,9). Reports on causes of death in cohorts of patients diagnosed during late adolescence or young adulthood, with long-term follow-up, are less frequent (10). […] Adherence to treatment during this age is poor and the risk of acute diabetic complications is high (1316). Mortality may differ between those with diabetes diagnosed during this period of life and those diagnosed during childhood.”

“Mortality was between four and five times higher than in the general population […]. The excess mortality was similar for men […] and women […]. SMR was higher in the lower age bands — 6.7 (95% CI 3.9–11.5) at 15–24 years and 7.3 (95% CI 5.2–10.1) at 25–34 years — compared with the higher age bands: 3.7 (95% CI 2.7–4.9) at 45–54 years and 3.9 (95% CI 2.6–5.8) at 55–65 years […]. The Cox regression model showed that the risk of death increased significantly by age at diagnosis (HR 1.1; 95% CI 1.1–1.2; P < 0.001) and was eight to nine times higher if ESRD was present (HR 8.7; 95% CI 4.8–15.5; P < 0.0001). […] the underlying cause of death was diabetes in 57 individuals (39.0%), circulatory in 22 (15.1%), cancer in 18 (12.3%), accidents or intoxications in 20 (13.7%), suicide in 8 (5.5%), and any other cause in 21 (14.4%) […] In addition, diabetes contributed to death in 29.5% (n = 43) and CVD contributed to death in 10.9% (n = 29) of the 146 cases. Diabetes was mentioned on the death certificate for 68.2% of the cohort but for only 30.0% of the violent deaths. […] In 60% (88/146) of the cases the review committee considered death to be related to diabetes, whereas in 40% (58/146) the cause was unrelated to diabetes or had an unknown relation to diabetes. According to the clinical committee, acute complications caused death in 20.5% (30/146) of the cases; 20 individuals died as a result of DKA and 10 from hypoglycemia. […] Chronic complications caused the largest proportion of deaths (47/146; 32.2%) and increased with increasing duration of diabetes […]. Among individuals dying as a result of chronic complications (n = 47), CVD caused death in 94% (n = 44) and renal failure in 6% (n = 3). ESRD contributed to death in 22.7% (10/44) of those dying from CVD. Cardiovascular death occurred at mortality rates seven times higher than those in the general population […]. ESRD caused or contributed to death in 13 of 14 cases, when present.”

“Violence (intoxications, accidents, and suicides) was the leading cause of death before 10 years’ duration of diabetes; thereafter it was only a minor cause […] Insulin was used in two of seven suicides. […] According to the available medical records and autopsy reports, about 20% (29/146) of the deceased misused alcohol. In 15% (22/146) alcohol-related ICD-10 codes were listed on the death certificate (18% [19/106] of men and 8% [3/40] of women). In 10 cases the cause of death was uncertain but considered to be related to alcohol or diabetes […] The SMR for alcohol-related death was high when considering the underlying cause of death (5.0; 95% CI 2.5–10.0), and even higher when considering all alcohol-related ICD-10 codes listed on the death certificate (6.8; 95% CI 4.5–10.3). The cause of death was associated with alcohol in 21.8% (19/87) of those who died with less than 20 years’ diabetes duration. Drug abuse was noted on the death certificate in only two cases.”

“During follow-up, 33 individuals (4.6%; 22 men and 11 women) developed ESRD as a result of diabetic nephropathy. Mean time from diagnosis of diabetes to ESRD was 23.6 years (range 14.2–33.5 years). Cumulative incidence of ESRD by years since diagnosis of diabetes was 1.4% (95% CI 0.7–2.7) at 20 years and 4.8% (95% CI 3.4–6.9) at 30 years.”

“This study highlights three important findings. First, among individuals who were diagnosed with type 1 diabetes in late adolescence and early adulthood and had good access to health care, and who were followed for 30 years, mortality was four to five times that of the general population. Second, 15% of all deaths were associated with alcohol, and the SMR for alcohol-related deaths was 6.8. Third, there was a relatively low cumulative incidence of ESRD (4.8%) 30 years after the diagnosis of diabetes.

We report mortality higher than those from a large, population-based study from Finland that found cumulative mortality around 6% at 20 years’ and 15% at 30 years’ duration of diabetes among a population with age at onset and year of diagnosis similar to those in our cohort (10). The corresponding numbers in our cohort were 12% and 18%, respectively; the discrepancy was particularly high at 20 years. The SMR in the Finnish cohort was lower than that in our cohort (2.6–3.0 vs. 3.7–5.1), and those authors reported the SMR to be lower in late-onset diabetes (at age 15–29 years) compared with early-onset diabetes (at age 23). The differences between the Norwegian and Finnish data are difficult to explain since both reports are from countries with good access to health care and a high incidence of type 1 diabetes.”

However the reason for the somewhat different SMRs in these two reasonably similar countries may actually be quite simple – the important variable may be alcohol:

“Finland and Norway are appropriate to compare because they share important population and welfare characteristics. There are, however, significant differences in drinking levels and alcohol-related mortality: the Finnish population consumes more alcohol and the Norwegian population consumes less. The mortality rates for deaths related to alcohol are about three to four times higher in Finland than in Norway (30). […] The markedly higher SMR in our cohort can probably be explained by the lower mortality rates for alcohol-related mortality in the general population. […] In conclusion, the high mortality reported in this cohort with an onset of diabetes in late adolescence and young adulthood draws attention to people diagnosed during a vulnerable period of life. Both acute and chronic complications cause substantial premature mortality […] Our study suggests that increased awareness of alcohol-related death should be encouraged in clinics providing health care to this group of patients.”

April 23, 2017 Posted by | Diabetes, Economics, Epidemiology, Medicine, Nephrology, Neurology, Papers, Pharmacology, Psychology | Leave a comment

A few autism papers

i. The anterior insula in autism: Under-connected and under-examined.

“While the past decade has witnessed a proliferation of neuroimaging studies of autism, theoretical approaches for understanding systems-level brain abnormalities remain poorly developed. We propose a novel anterior insula-based systems-level model for investigating the neural basis of autism, synthesizing recent advances in brain network functional connectivity with converging evidence from neuroimaging studies in autism. The anterior insula is involved in interoceptive, affective and empathic processes, and emerging evidence suggests it is part of a “salience network” integrating external sensory stimuli with internal states. Network analysis indicates that the anterior insula is uniquely positioned as a hub mediating interactions between large-scale networks involved in externally- and internally-oriented cognitive processing. A recent meta-analysis identifies the anterior insula as a consistent locus of hypoactivity in autism. We suggest that dysfunctional anterior insula connectivity plays an important role in autism. […]

Increasing evidence for abnormal brain connectivity in autism comes from studies using functional connectivity measures […] These findings support the hypothesis that under-connectivity between specific brain regions is a characteristic feature of ASD. To date, however, few studies have examined functional connectivity within and between key large-scale canonical brain networks in autism […] The majority of published studies to date have examined connectivity of specific individual brain regions, without a broader theoretically driven systems-level approach.

We propose that a systems-level approach is critical for understanding the neurobiology of autism, and that the anterior insula is a key node in coordinating brain network interactions, due to its unique anatomy, location, function, and connectivity.”

ii. Romantic Relationships and Relationship Satisfaction Among Adults With Asperger Syndrome and High‐Functioning Autism.

“Participants, 31 recruited via an outpatient clinic and 198 via an online survey, were asked to answer a number of self-report questionnaires. The total sample comprised 229 high-functioning adults with ASD (40% males, average age: 35 years). […] Of the total sample, 73% indicated romantic relationship experience and only 7% had no desire to be in a romantic relationship. ASD individuals whose partner was also on the autism spectrum were significantly more satisfied with their relationship than those with neurotypical partners. Severity of autism, schizoid symptoms, empathy skills, and need for social support were not correlated with relationship status. […] Our findings indicate that the vast majority of high-functioning adults with ASD are interested in romantic relationships.”

Those results are very different from other results in the field – for example: “[a] meta-analysis of follow-up studies examining outcomes of ASD individuals revealed that, [o]n average only 14% of the individuals included in the reviewed studies were married or ha[d] a long-term, intimate relationship (Howlin, 2012)” – and one major reason is that they only include high-functioning autistics. I feel sort of iffy about the validity of the selection method used for procuring the online sample, this may also be a major factor (almost one third of them had a university degree so this is definitely not a random sample of high-functioning autistics; ‘high-functioning’ autistics are not that high-functioning in the general setting. Also, the sex ratio is very skewed as 60% of the participants in the study were female. A sex ratio like that may not sound like a big problem, but it is a major problem because a substantial majority of individuals with mild autism are males. Whereas the sex ratio is almost equal in the context of syndromic ASD, non-syndromic ASD is much more prevalent in males, with sex ratios approaching 1:7 in milder cases (link). These people are definitely looking at the milder cases, which means that a sample which skews female will not be remotely similar to most random samples of such individuals taken in the community setting. And this matters because females do better than males. A discussion can be had about to which extent women are under-diagnosed, but I have not seen data convincing me this is a major problem. It’s important to keep in mind in that context that the autism diagnosis is not based on phenotype alone, but on a phenotype-environment interaction; if you have what might be termed ‘an autistic phenotype’ but you are not suffering any significant ill effects as a result of this because you’re able to compensate relatively well (i.e. you are able to handle ‘the environment’ reasonably well despite the neurological makeup you’ve ended up with), you should not get an autism diagnosis – a diagnostic requirement is ‘clinically significant impairment in functioning’.

Anyway some more related data from the publication:

“Studies that analyze outcomes exclusively for ASD adults without intellectual impairment are rare. […] Engström, Ekström, and Emilsson (2003) recruited previous patients with an ASD diagnosis from four psychiatric clinics in Sweden. They reported that 5 (31%) of 16 adults with ASD had ”some form of relation with a partner.” Hofvander et al. (2009) analyzed data from 122 participants who had been referred to outpatient clinics for autism diagnosis. They found that 19 (16%) of all participants had lived in a long-term relationship.
Renty and Roeyers (2006) […] reported that at the time of the[ir] study 19% of 58 ASD adults had a romantic relationship and 8.6% were married or living with a partner. Cederlund, Hagberg, Billstedt, Gillberg, and Gillberg (2008) conducted a follow-up study of male individuals (aged 16–36 years) who had been diagnosed with Asperger syndrome at least 5 years before. […] at the time of the study, three (4%) [out of 76 male ASD individuals] of them were living in a long-term romantic relationship and 10 (13%) had had romantic relationships in the past.”

A few more data and observations from the study:

“A total of 166 (73%) of the 229 participants endorsed currently being in a romantic relationship or having a history of being in a relationship; 100 (44%) reported current involvement in a romantic relationship; 66 (29%) endorsed that they were currently single but have a history of involvement in a romantic relationship; and 63 (27%) participants did not have any experience with romantic relationships. […] Participants without any romantic relationship experience were significantly more likely to be male […] According to participants’ self-report, one fifth (20%) of the 100 participants who were currently involved in a romantic relationship were with an ASD partner. […] Of the participants who were currently single, 65% said that contact with another person was too exhausting for them, 61% were afraid that they would not be able to fulfil the expectations of a romantic partner, and 57% said that they did not know how they could find and get involved with a partner; and 50% stated that they did not know how a romantic relationship works or how they would be expected to behave in a romantic relationship”

“[P]revious studies that exclusively examined adults with ASD without intellectual impairment reported lower levels of romantic relationship experience than the current study, with numbers varying between 16% and 31% […] The results of our study can be best compared with the results of Hofvander et al. (2009) and Renty and Roeyers (2006): They selected their samples […] using methods that are comparable to ours. Hofvander et al. (2009) found that 16% of their participants have had romantic relationship experience in the past, compared to 29% in our sample; and Renty and Roeyers (2006) report that 28% of their participants were either married or engaged in a romantic relationship at the time of their study, compared to 44% in our study. […] Compared to typically developed individuals the percentage of ASD individuals with a romantic relationship partner is relatively low (Weimann, 2010). In the group aged 27–59 years, 68% of German males live together with a partner, 27% are single, and 5% still live with their parents. In the same age group, 73% of all females live with a partner, 26% live on their own, and 2% still live with their parents.”

“As our results show, it is not the case that male ASD individuals do not feel a need for romantic relationships. In fact, the contrary is true. Single males had a greater desire to be in a romantic relationship than single females, and males were more distressed than females about not being in a romantic relationship.” (…maybe in part because the females who were single were more likely than the males who were single to be single by choice?)

“Our findings showed that being with a partner who also has an ASD diagnosis makes a romantic relationship more satisfying for ASD individuals. None of the participants, who had been with a partner in the past but then separated, had been together with an ASD partner. This might indicate that once a person with ASD has found a partner who is also on the spectrum, a relationship might be very stable and long lasting.”

Reward Processing in Autism.

“The social motivation hypothesis of autism posits that infants with autism do not experience social stimuli as rewarding, thereby leading to a cascade of potentially negative consequences for later development. […] Here we use functional magnetic resonance imaging to examine social and monetary rewarded implicit learning in children with and without autism spectrum disorders (ASD). Sixteen males with ASD and sixteen age- and IQ-matched typically developing (TD) males were scanned while performing two versions of a rewarded implicit learning task. In addition to examining responses to reward, we investigated the neural circuitry supporting rewarded learning and the relationship between these factors and social development. We found diminished neural responses to both social and monetary rewards in ASD, with a pronounced reduction in response to social rewards (SR). […] Moreover, we show a relationship between ventral striatum activity and social reciprocity in TD children. Together, these data support the hypothesis that children with ASD have diminished neural responses to SR, and that this deficit relates to social learning impairments. […] When we examined the general neural response to monetary and social reward events, we discovered that only TD children showed VS [ventral striatum] activity for both reward types, whereas ASD children did not demonstrate a significant response to either monetary or SR. However, significant between-group differences were shown only for SR, suggesting that children with ASD may be specifically impaired on processing SR.”

I’m not quite sure I buy that the methodology captures what it is supposed to capture (“The SR feedback consisted of a picture of a smiling woman with the words “That’s Right!” in green text for correct trials and a picture of the same woman with a sad face along with the words “That’s Wrong” in red text for incorrect trials”) (this is supposed to be the ‘social reward feedback’), but on the other hand: “The chosen reward stimuli, faces and coins, are consistent with those used in previous studies of reward processing” (so either multiple studies are of dubious quality, or this kind of method actually ‘works’ – but I don’t know enough about the field to tell which of the two conclusions apply).

iv. The Social Motivation Theory of Autism.

“The idea that social motivation deficits play a central role in Autism Spectrum Disorders (ASD) has recently gained increased interest. This constitutes a shift in autism research, which has traditionally focused more intensely on cognitive impairments, such as Theory of Mind deficits or executive dysfunction, while granting comparatively less attention to motivational factors. This review delineates the concept of social motivation and capitalizes on recent findings in several research areas to provide an integrated picture of social motivation at the behavioral, biological and evolutionary levels. We conclude that ASD can be construed as an extreme case of diminished social motivation and, as such, provides a powerful model to understand humans’ intrinsic drive to seek acceptance and avoid rejection.”

v. Stalking, and Social and Romantic Functioning Among Adolescents and Adults with Autism Spectrum Disorder.

“We examine the nature and predictors of social and romantic functioning in adolescents and adults with ASD. Parental reports were obtained for 25 ASD adolescents and adults (13-36 years), and 38 typical adolescents and adults (13-30 years). The ASD group relied less upon peers and friends for social (OR = 52.16, p < .01) and romantic learning (OR = 38.25, p < .01). Individuals with ASD were more likely to engage in inappropriate courting behaviours (χ2 df = 19 = 3168.74, p < .001) and were more likely to focus their attention upon celebrities, strangers, colleagues, and ex-partners (χ2 df = 5 =2335.40, p < .001), and to pursue their target longer than controls (t = -2.23, df = 18.79, p < .05).”

“Examination of relationships the individuals were reported to have had with the target of their social or romantic interest, indicated that ASD adolescents and adults sought to initiate fewer social and romantic relationships but across a wider variety of people, such as strangers, colleagues, acquaintances, friends, ex-partners, and celebrities. […] typically developing peers […] were more likely to target colleagues, acquaintances, friends, and ex-partners in their relationship attempts, whilst the ASD group targeted these less frequently than expected, and attempted to initiate relationships significantly more frequently than is typical, with strangers and celebrities. […] In attempting to pursue and initiate social and romantic relationships, the ASD group were reported to display a much wider variety of courtship behaviours than the typical group. […] ASD adolescents and adults were more likely to touch the person of interest inappropriately, believe that the target must reciprocate their feelings, show obsessional interest, make inappropriate comments, monitor the person’s activities, follow them, pursue them in a threatening manner, make threats against the person, and threaten self-harm. ASD individuals displayed the majority of the behaviours indiscriminately across all types of targets. […] ASD adolescents and adults were also found […] to persist in their relationship pursuits for significantly longer periods of time than typical adolescents and adults when they received a negative or no response from the person or their family.”

April 4, 2017 Posted by | autism, Neurology, Papers, Psychology | Leave a comment

Diabetes and the brain (IV)

Here’s one of my previous posts in the series about the book. In this post I’ll cover material dealing with two acute hyperglycemia-related diabetic complications (DKA and HHS – see below…) as well as multiple topics related to diabetes and stroke. I’ll start out with a few quotes from the book about DKA and HHS:

“DKA [diabetic ketoacidosis] is defined by a triad of hyperglycemia, ketosis, and acidemia and occurs in the absolute or near-absolute absence of insulin. […] DKA accounts for the bulk of morbidity and mortality in children with T1DM. National population-based studies estimate DKA mortality at 0.15% in the United States (4), 0.18–0.25% in Canada (4, 5), and 0.31% in the United Kingdom (6). […] Rates reach 25–67% in those who are newly diagnosed (4, 8, 9). The rates are higher in younger children […] The risk of DKA among patients with pre-existing diabetes is 1–10% annual per person […] DKA can present with mild-to-severe symptoms. […] polyuria and polydipsia […] patients may present with signs of dehydration, such as tachycardia and dry mucus membranes. […] Vomiting, abdominal pain, malaise, and weight loss are common presenting symptoms […] Signs related to the ketoacidotic state include hyperventilation with deep breathing (Kussmaul’s respiration) which is a compensatory respiratory response to an underlying metabolic acidosis. Acetonemia may cause a fruity odor to the breath. […] Elevated glucose levels are almost always present; however, euglycemic DKA has been described (19). Anion-gap metabolic acidosis is the hallmark of this condition and is caused by elevated ketone bodies.”

“Clinically significant cerebral edema occurs in approximately 1% of patients with diabetic ketoacidosis […] DKA-related cerebral edema may represent a continuum. Mild forms resulting in subtle edema may result in modest mental status abnormalities whereas the most severe manifestations result in overt cerebral injury. […] Cerebral edema typically presents 4–12 h after the treatment for DKA is started (28, 29), but can occur at any time. […] Increased intracranial pressure with cerebral edema has been recognized as the leading cause of morbidity and mortality in pediatric patients with DKA (59). Mortality from DKA-related cerebral edema in children is high, up to 90% […] and accounts for 60–90% of the mortality seen in DKA […] many patients are left with major neurological deficits (28, 31, 35).”

“The hyperosmolar hyperglycemic state (HHS) is also an acute complication that may occur in patients with diabetes mellitus. It is seen primarily in patients with T2DM and has previously been referred to as “hyperglycemic hyperosmolar non-ketotic coma” or “hyperglycemic hyperosmolar non-ketotic state” (13). HHS is marked by profound dehydration and hyperglycemia and often by some degree of neurological impairment. The term hyperglycemic hyperosmolar state is used because (1) ketosis may be present and (2) there may be varying degrees of altered sensorium besides coma (13). Like DKA, the basic underlying disorder is inadequate circulating insulin, but there is often enough insulin to inhibit free fatty acid mobilization and ketoacidosis. […] Up to 20% of patients diagnosed with HHS do not have a previous history of diabetes mellitus (14). […] Kitabchi et al. estimated the rate of hospital admissions due to HHS to be lower than DKA, accounting for less than 1% of all primary diabetic admissions (13). […] Glucose levels rise in the setting of relative insulin deficiency. The low levels of circulating insulin prevent lipolysis, ketogenesis, and ketoacidosis (62) but are unable to suppress hyperglycemia, glucosuria, and water losses. […] HHS typically presents with one or more precipitating factors, similar to DKA. […] Acute infections […] account for approximately 32–50% of precipitating causes (13). […] The mortality rates for HHS vary between 10 and 20% (14, 93).”

It should perhaps be noted explicitly that the mortality rates for these complications are particularly high in the settings of either very young individuals (DKA) or in elderly individuals (HHS) who might have multiple comorbidities. Relatedly HHS often develops acutely specifically in settings where the precipitating factor is something really unpleasant like pneumonia or a cardiovascular event, so a high-ish mortality rate is perhaps not that surprising. Nor is it surprising that very young brains are particularly vulnerable in the context of DKA (I already discussed some of the research on these matters in some detail in an earlier post about this book).

This post to some extent covered the topic of ‘stroke in general’, however I wanted to include here also some more data specifically on diabetes-related matters about this topic. Here’s a quote to start off with:

“DM [Diabetes Mellitus] has been consistently shown to represent a strong independent risk factor of ischemic stroke. […] The contribution of hyperglycemia to increased stroke risk is not proven. […] the relationship between hyperglycemia and stroke remains subject of debate. In this respect, the association between hyperglycemia and cerebrovascular disease is established less strongly than the association between hyperglycemia and coronary heart disease. […] The course of stroke in patients with DM is characterized by higher mortality, more severe disability, and higher recurrence rate […] It is now well accepted that the risk of stroke in individuals with DM is equal to that of individuals with a history of myocardial infarction or stroke, but no DM (24–26). This was confirmed in a recently published large retrospective study which enrolled all inhabitants of Denmark (more than 3 million people out of whom 71,802 patients with DM) and were followed-up for 5 years. In men without DM the incidence of stroke was 2.5 in those without and 7.8% in those with prior myocardial infarction, whereas in patients with DM it was 9.6 in those without and 27.4% in those with history of myocardial infarction. In women the numbers were 2.5, 9.0, 10.0, and 14.2%, respectively (22).

That study incidentally is very nice for me in particular to know about, given that I am a Danish diabetic. I do not here face any of the usual tiresome questions about ‘external validity’ and issues pertaining to ‘extrapolating out of sample’ – not only is it quite likely I’ve actually looked at some of the data used in that analysis myself, I also know that I am almost certainly one of the people included in the analysis. Of course you need other data as well to assess risk (e.g. age, see the previously linked post), but this is pretty clean as far as it goes. Moving on…

“The number of deaths from stroke attributable to DM is highest in low-and-middle-income countries […] the relative risk conveyed by DM is greater in younger subjects […] It is not well known whether type 1 or type 2 DM affects stroke risk differently. […] In the large cohort of women enrolled in the Nurses’ Health Study (116,316 women followed for up to 26 years) it was shown that the incidence of total stroke was fourfold higher in women with type 1 DM and twofold higher among women with type 2 DM than for non-diabetic women (33). […] The impact of DM duration as a stroke risk factor has not been clearly defined. […] In this context it is important to note that the actual duration of type 2 DM is difficult to determine precisely […and more generally: “the date of onset of a certain chronic disease is a quantity which is not defined as precisely as mortality“, as Yashin et al. put it – I also talked about this topic in my previous post, but it’s important when you’re looking at these sorts of things and is worth reiterating – US]. […] Traditional risk factors for stroke such as arterial hypertension, dyslipidemia, atrial fibrillation, heart failure, and previous myocardial infarction are more common in people with DM […]. However, the impact of DM on stroke is not just due to the higher prevalence of these risk factors, as the risk of mortality and morbidity remains over twofold increased after correcting for these factors (4, 37). […] It is informative to distinguish between factors that are non-specific and specific to DM. DM-specific factors, including chronic hyperglycemia, DM duration, DM type and complications, and insulin resistance, may contribute to an elevated stroke risk either by amplification of the harmful effect of other “classical” non-specific risk factors, such as hypertension, or by acting independently.”

More than a few variables are known to impact stroke risk, but the fact that many of the risk factors are related to each other (‘fat people often also have high blood pressure’) makes it hard to figure out which variables are most important, how they interact with each other, etc., etc. One might in that context perhaps conceptualize the metabolic syndrome (-MS) as a sort of indicator variable indicating whether a relatively common set of such related potential risk factors of interest are present or not – it is worth noting in that context that the authors include in the text the observation that: “it is yet uncertain if the whole concept of the MS entails more than its individual components. The clustering of risk factors complicates the assessment of the contribution of individual components to the risk of vascular events, as well as assessment of synergistic or interacting effects.” MS confers a two-threefold increased stroke risk, depending on the definition and the population analyzed, so there’s definitely some relevant stuff included in that box, but in the context of developing new treatment options and better assess risk it might be helpful to – to put it simplistically – know if variable X is significantly more important than variable Y (and how the variables interact, etc., etc.). But this sort of information is hard to get.

There’s more than one type of stroke, and the way diabetes modifies the risk of various stroke types is not completely clear:

“Most studies have consistently shown that DM is an important risk factor for ischemic stroke, while the incidence of hemorrhagic stroke in subjects with DM does not seem to be increased. Consequently, the ratio of ischemic to hemorrhagic stroke is higher in patients with DM than in those stroke patients without DM [recall the base rates I’ve mentioned before in the coverage of this book: 80% of strokes are ischemic strokes in Western countries, and 15 % hemorrhagic] […] The data regarding an association between DM and the risk of hemorrhagic stroke are quite conflicting. In the most series no increased risk of cerebral hemorrhage was found (10, 101), and in the Copenhagen Stroke Registry, hemorrhagic stroke was even six times less frequent in diabetic patients than in non-diabetic subjects (102). […] However, in another prospective population-based study DM was associated with an increased risk of primary intracerebral hemorrhage (103). […] The significance of DM as a risk factor of hemorrhagic stroke could differ depending on ethnicity of subjects or type of DM. In the large Nurses’ Health Study type 1 DM increased the risk of hemorrhagic stroke by 3.8 times while type 2 DM did not increase such a risk (96). […] It is yet unclear if DM predominantly predisposes to either large or small vessel ischemic stroke. Nevertheless, lacunar stroke (small, less than 15mm in diameter infarction, cyst-like, frequently multiple) is considered to be the typical type of stroke in diabetic subjects (105–107), and DM may be present in up to 28–43% of patients with cerebral lacunar infarction (108–110).”

The Danish results mentioned above might not be as useful to me as they were before if the type is important, because the majority of those diabetics included were type 2 diabetics. I know from personal experience that it is difficult to type-identify diabetics using the Danish registry data available if you want to work with population-level data, and any type of scheme attempting this will be subject to potentially large misidentification problems. Some subgroups can be presumably correctly identified using diagnostic codes, but a very large number of individuals will be left out of the analyses if you only rely on identification strategies where you’re (at least reasonably?) certain about the type. I’ve worked on these identification problems during my graduate work so perhaps a few more things are worth mentioning here. In the context of diabetic subgroup analyses, misidentification is in general a much larger problem in the context of type 1 results than in the context of type 2 results; unless the study design takes the large prevalence difference of the two conditions into account, the type 1 sample will be much smaller than the type 2 sample in pretty much all analytical contexts, so a small number of misidentified type 2 individuals can have large impacts on the results of the type 1 sample. Type 1s misidentified as type 2 individuals is in general to be expected to be a much smaller problem in terms of the validity of the type 2 analysis; misidentification of that type will cause a loss of power in the context of the type 1 subgroup analysis, which is already low to start with (and it’ll also make the type 1 subgroup analysis even more vulnerable to misidentified type 2s), but it won’t much change the results of the type 2 subgroup analysis in any significant way. Relatedly, even if enough type 2 patients are misidentified to cause problems with the interpretation of the type 1 subgroup analysis, this would not on its own be a good reason to doubt the results of the type 2 subgroup analysis. Another thing to note in terms of these things is that given that misidentification will tend to lead to ‘mixing’, i.e. it’ll make the subgroup results look similar, when outcomes are not similar in the type 1 and the type 2 individuals then this might be taken to be an indicator that something potentially interesting might be going on, because most analyses will struggle with some level of misidentification which will tend to reduce the power of tests of group differences.

What about stroke outcomes? A few observations were included on that topic above, but the book has a lot more stuff on that – some observations on this topic:

“DM is an independent risk factor of death from stroke […]. Tuomilehto et al. (35) calculated that 16% of all stroke mortality in men and 33% in women could be directly attributed to DM. Patients with DM have higher hospital and long-term stroke mortality, more pronounced residual neurological deficits, and more severe disability after acute cerebrovascular accidents […]. The 1-year mortality rate, for example, was twofold higher in diabetic patients compared to non-diabetic subjects (50% vs. 25%) […]. Only 20% of people with DM survive over 5 years after the first stroke and half of these patients die within the first year (36, 128). […] The mechanisms underlying the worse outcome of stroke in diabetic subjects are not fully understood. […] Regarding prevention of stroke in patients with DM, it may be less relevant than in non-DM subjects to distinguish between primary and secondary prevention as all patients with DM are considered to be high-risk subjects regardless of the history of cerebrovascular accidents or the presence of clinical and subclinical vascular lesions. […] The influence of the mode of antihyperglycemic treatment on the risk of stroke is uncertain.

Control of blood pressure is very important in the diabetic setting:

“There are no doubts that there is a linear relation between elevated systolic blood pressure and the risk of stroke, both in people with or without DM. […] Although DM and arterial hypertension represent significant independent risk factors for stroke if they co-occur in the same patient the risk increases dramatically. A prospective study of almost 50 thousand subjects in Finland followed up for 19 years revealed that the hazard ratio for stroke incidence was 1.4, 2.0, 2.5, 3.5, and 4.5 and for stroke mortality was 1.5, 2.6, 3.1, 5.6, and 9.3, respectively, in subjects with an isolated modestly elevated blood pressure (systolic 140–159/diastolic 90–94 mmHg), isolated more severe hypertension (systolic >159 mmHg, diastolic >94 mmHg, or use of antihypertensive drugs), with isolated DM only, with both DM and modestly elevated blood pressure, and with both DM and more severe hypertension, relative to subjects without either of the risk factors (168). […] it remains unclear whether some classes of antihypertensive agents provide a stronger protection against stroke in diabetic patients than others. […] effective antihypertensive treatment is highly beneficial for reduction of stroke risk in diabetic patients, but the advantages of any particular class of antihypertensive medications are not substantially proven.”

Treatment of dyslipidemia is also very important, but here it does seem to matter how you treat it:

“It seems that the beneficial effect of statins is dose-dependent. The lower the LDL level that is achieved the stronger the cardiovascular protection. […] Recently, the results of the meta-analysis of 14 randomized trials of statins in 18,686 patients with DM had been published. It was calculated that statins use in diabetic patients can result in a 21% reduction of the risk of any stroke per 1 mmol/l reduction of LDL achieved […] There is no evidence from trials that supports efficacy of fibrates for stroke prevention in diabetic patients. […] No reduction of stroke risk by fibrates was shown also in a meta-analysis of eight trials enrolled 12,249 patients with type 2 DM (204).”

Antiplatelets?

“Significant reductions in stroke risk in diabetic patients receiving antiplatelet therapy were found in large-scale controlled trials (205). It appears that based on the high incidence of stroke and prevalence of stroke risk factors in the diabetic population the benefits of routine aspirin use for primary and secondary stroke prevention outweigh its potential risk of hemorrhagic stroke especially in patients older than 30 years having at least one additional risk factor (206). […] both guidelines issued by the AHA/ADA or the ESC/EASD on the prevention of cardiovascular disease in patients with DM support the use of aspirin in a dose of 50–325 mg daily for the primary prevention of stroke in subjects older than 40 years of age and additional risk factors, such as DM […] The newer antiplatelet agent, clopidogrel, was more efficacious in prevention of ischemic stroke than aspirin with greater risk reduction in the diabetic cohort especially in those treated with insulin compared to non-diabetics in CAPRIE trial (209). However, the combination of aspirin and clopidogrel does not appear to be more efficacious and safe compared to clopidogrel or aspirin alone”.

When you treat all risk factors aggressively, it turns out that the elevated stroke risk can be substantially reduced. Again the data on this stuff is from Denmark:

“Gaede et al. (216) have shown in the Steno 2 study that intensive multifactorial intervention aimed at correction of hyperglycemia, hypertension, dyslipidemia, and microalbuminuria along with aspirin use resulted in a reduction of cardiovascular morbidity including non-fatal stroke […] recently the results of the extended 13.3 years follow-up of this study were presented and the reduction of cardiovascular mortality by 57% and morbidity by 59% along with the reduction of the number of non-fatal stroke (6 vs. 30 events) in intensively treated group was convincingly demonstrated (217). Antihypertensive, hypolipidemic treatment, use of aspirin should thus be recommended as either primary or secondary prevention of stroke for patients with DM.”

March 3, 2017 Posted by | Books, Cardiology, Diabetes, Epidemiology, Medicine, Neurology, Pharmacology, Statistics | Leave a comment

Biodemography of aging (I)

“The goal of this monograph is to show how questions about the connections between and among aging, health, and longevity can be addressed using the wealth of available accumulated knowledge in the field, the large volumes of genetic and non-genetic data collected in longitudinal studies, and advanced biodemographic models and analytic methods. […] This monograph visualizes aging-related changes in physiological variables and survival probabilities, describes methods, and summarizes the results of analyses of longitudinal data on aging, health, and longevity in humans performed by the group of researchers in the Biodemography of Aging Research Unit (BARU) at Duke University during the past decade. […] the focus of this monograph is studying dynamic relationships between aging, health, and longevity characteristics […] our focus on biodemography/biomedical demography meant that we needed to have an interdisciplinary and multidisciplinary biodemographic perspective spanning the fields of actuarial science, biology, economics, epidemiology, genetics, health services research, mathematics, probability, and statistics, among others.”

The quotes above are from the book‘s preface. In case this aspect was not clear from the comments above, this is the kind of book where you’ll randomly encounter sentences like these:

The simplest model describing negative correlations between competing risks is the multivariate lognormal frailty model. We illustrate the properties of such model for the bivariate case.

“The time-to-event sub-model specifies the latent class-specific expressions for the hazard rates conditional on the vector of biomarkers Yt and the vector of observed covariates X …”

…which means that some parts of the book are really hard to blog; it simply takes more effort to deal with this stuff here than it’s worth. As a result of this my coverage of the book will not provide a remotely ‘balanced view’ of the topics covered in it; I’ll skip a lot of the technical stuff because I don’t think it makes much sense to cover specific models and algorithms included in the book in detail here. However I should probably also emphasize while on this topic that although the book is in general not an easy read, it’s hard to read because ‘this stuff is complicated’, not because the authors are not trying. The authors in fact make it clear already in the preface that some chapters are more easy to read than are others and that some chapters are actually deliberately written as ‘guideposts and way-stations‘, as they put it, in order to make it easier for the reader to find the stuff in which he or she is most interested (“the interested reader can focus directly on the chapters/sections of greatest interest without having to read the entire volume“) – they have definitely given readability aspects some thought, and I very much like the book so far; it’s full of great stuff and it’s very well written.

I have had occasion to question a few of the observations they’ve made, for example I was a bit skeptical about a few of the conclusions they drew in chapter 6 (‘Medical Cost Trajectories and Onset of Age-Associated Diseases’), but this was related to what some would certainly consider to be minor details. In the chapter they describe a model of medical cost trajectories where the post-diagnosis follow-up period is 20 months; this is in my view much too short a follow-up period to draw conclusions about medical cost trajectories in the context of type 2 diabetes, one of the diseases included in the model, which I know because I’m intimately familiar with the literature on that topic; you need to look 7-10 years ahead to get a proper sense of how this variable develops over time – and it really is highly relevant to include those later years, because if you do not you may miss out on a large proportion of the total cost given that a substantial proportion of the total cost of diabetes relate to complications which tend to take some years to develop. If your cost analysis is based on a follow-up period as short as that of that model you may also on a related note draw faulty conclusions about which medical procedures and -subsidies are sensible/cost effective in the setting of these patients, because highly adherent patients may be significantly more expensive in a short run analysis like this one (they show up to their medical appointments and take their medications…) but much cheaper in the long run (…because they take their medications they don’t go blind or develop kidney failure). But as I say, it’s a minor point – this was one condition out of 20 included in the analysis they present, and if they’d addressed all the things that pedants like me might take issue with, the book would be twice as long and it would likely no longer be readable. Relatedly, the model they discuss in that chapter is far from unsalvageable; it’s just that one of the components of interest –  ‘the difference between post- and pre-diagnosis cost levels associated with an acquired comorbidity’ – in the case of at least one disease is highly unlikely to be correct (given the authors’ interpretation of the variable), because there’s some stuff of relevance which the model does not include. I found the model quite interesting, despite the shortcomings, and the results were definitely surprising. (No, the above does not in my opinion count as an example of coverage of a ‘specific model […] in detail’. Or maybe it does, but I included no equations. On reflection I probably can’t promise much more than that, sometimes the details are interesting…)

Anyway, below I’ve added some quotes from the first few chapters of the book and a few remarks along the way.

“The genetics of aging, longevity, and mortality has become the subject of intensive analyses […]. However, most estimates of genetic effects on longevity in GWAS have not reached genome-wide statistical significance (after applying the Bonferroni correction for multiple testing) and many findings remain non-replicated. Possible reasons for slow progress in this field include the lack of a biologically-based conceptual framework that would drive development of statistical models and methods for genetic analyses of data [here I was reminded of Burnham & Anderson’s coverage, in particular their criticism of mindless ‘Let the computer find out’-strategies – the authors of that chapter seem to share their skepticism…], the presence of hidden genetic heterogeneity, the collective influence of many genetic factors (each with small effects), the effects of rare alleles, and epigenetic effects, as well as molecular biological mechanisms regulating cellular functions. […] Decades of studies of candidate genes show that they are not linked to aging-related traits in a straightforward fashion (Finch and Tanzi 1997; Martin 2007). Recent genome-wide association studies (GWAS) have supported this finding by showing that the traits in late life are likely controlled by a relatively large number of common genetic variants […]. Further, GWAS often show that the detected associations are of tiny size (Stranger et al. 2011).”

I think this ties in well with what I’ve previously read on these and related topics – see e.g. the second-last paragraph quoted in my coverage of Richard Alexander’s book, or some of the remarks included in Roberts et al. Anyway, moving on:

“It is well known from epidemiology that values of variables describing physiological states at a given age are associated with human morbidity and mortality risks. Much less well known are the facts that not only the values of these variables at a given age, but also characteristics of their dynamic behavior during the life course are also associated with health and survival outcomes. This chapter [chapter 8 in the book, US] shows that, for monotonically changing variables, the value at age 40 (intercept), the rate of change (slope), and the variability of a physiological variable, at ages 40–60, significantly influence both health-span and longevity after age 60. For non-monotonically changing variables, the age at maximum, the maximum value, the rate of decline after reaching the maximum (right slope), and the variability in the variable over the life course may influence health-span and longevity. This indicates that such characteristics can be important targets for preventive measures aiming to postpone onsets of complex diseases and increase longevity.”

The chapter from which the quotes in the next two paragraphs are taken was completely filled with data from the Framingham Heart Study, and it was hard for me to know what to include here and what to leave out – so you should probably just consider the stuff I’ve included below as samples of the sort of observations included in that part of the coverage.

“To mediate the influence of internal or external factors on lifespan, physiological variables have to show associations with risks of disease and death at different age intervals, or directly with lifespan. For many physiological variables, such associations have been established in epidemiological studies. These include body mass index (BMI), diastolic blood pressure (DBP), systolic blood pressure (SBP), pulse pressure (PP), blood glucose (BG), serum cholesterol (SCH), hematocrit (H), and ventricular rate (VR). […] the connection between BMI and mortality risk is generally J-shaped […] Although all age patterns of physiological indices are non-monotonic functions of age, blood glucose (BG) and pulse pressure (PP) can be well approximated by monotonically increasing functions for both genders. […] the average values of body mass index (BMI) increase with age (up to age 55 for males and 65 for females), and then decline for both sexes. These values do not change much between ages 50 and 70 for males and between ages 60 and 70 for females. […] Except for blood glucose, all average age trajectories of physiological indices differ between males and females. Statistical analysis confirms the significance of these differences. In particular, after age 35 the female BMI increases faster than that of males. […] [When comparing women with less than or equal to 11 years of education [‘LE’] to women with 12 or more years of education [HE]:] The average values of BG for both groups are about the same until age 45. Then the BG curve for the LE females becomes higher than that of the HE females until age 85 where the curves intersect. […] The average values of BMI in the LE group are substantially higher than those among the HE group over the entire age interval. […] The average values of BG for the HE and LE males are very similar […] However, the differences between groups are much smaller than for females.”

They also in the chapter compared individuals with short life-spans [‘SL’, died before the age of 75] and those with long life-spans [‘LL’, 100 longest-living individuals in the relevant sample] to see if the variables/trajectories looked different. They did, for example: “trajectories for the LL females are substantially different from those for the SL females in all eight indices. Specifically, the average values of BG are higher and increase faster in the SL females. The entire age trajectory of BMI for the LL females is shifted to the right […] The average values of DBP [diastolic blood pressure, US] among the SL females are higher […] A particularly notable observation is the shift of the entire age trajectory of BMI for the LL males and females to the right (towards an older age), as compared with the SL group, and achieving its maximum at a later age. Such a pattern is markedly different from that for healthy and unhealthy individuals. The latter is mostly characterized by the higher values of BMI for the unhealthy people, while it has similar ages at maximum for both the healthy and unhealthy groups. […] Physiological aging changes usually develop in the presence of other factors affecting physiological dynamics and morbidity/mortality risks. Among these other factors are year of birth, gender, education, income, occupation, smoking, and alcohol use. An important limitation of most longitudinal studies is the lack of information regarding external disturbances affecting individuals in their day-today life.”

I incidentally noted while I was reading that chapter that a relevant variable ‘lurking in the shadows’ in the context of the male and female BMI trajectories might be changing smoking habits over time; I have not looked at US data on this topic, but I do know that the smoking patterns of Danish males and females during the latter half of the last century were markedly different and changed really quite dramatically in just a few decades; a lot more males than females smoked in the 60es, whereas the proportions of male- and female smokers today are much more similar, because a lot of males have given up smoking (I refer Danish readers to this blog post which I wrote some years ago on these topics). The authors of the chapter incidentally do look a little at data on smokers and they observe that smokers’ BMI are lower than non-smokers (not surprising), and that the smokers’ BMI curve (displaying the relationship between BMI and age) grows at a slower rate than the BMI curve of non-smokers (that this was to be expected is perhaps less clear, at least to me – the authors don’t interpret these specific numbers, they just report them).

The next chapter is one of the chapters in the book dealing with the SEER data I also mentioned not long ago in the context of my coverage of Bueno et al. Some sample quotes from that chapter below:

“To better address the challenge of “healthy aging” and to reduce economic burdens of aging-related diseases, key factors driving the onset and progression of diseases in older adults must be identified and evaluated. An identification of disease-specific age patterns with sufficient precision requires large databases that include various age-specific population groups. Collections of such datasets are costly and require long periods of time. That is why few studies have investigated disease-specific age patterns among older U.S. adults and there is limited knowledge of factors impacting these patterns. […] Information collected in U.S. Medicare Files of Service Use (MFSU) for the entire Medicare-eligible population of older U.S. adults can serve as an example of observational administrative data that can be used for analysis of disease-specific age patterns. […] In this chapter, we focus on a series of epidemiologic and biodemographic characteristics that can be studied using MFSU.”

“Two datasets capable of generating national level estimates for older U.S. adults are the Surveillance, Epidemiology, and End Results (SEER) Registry data linked to MFSU (SEER-M) and the National Long Term Care Survey (NLTCS), also linked to MFSU (NLTCS-M). […] The SEER-M data are the primary dataset analyzed in this chapter. The expanded SEER registry covers approximately 26 % of the U.S. population. In total, the Medicare records for 2,154,598 individuals are available in SEER-M […] For the majority of persons, we have continuous records of Medicare services use from 1991 (or from the time the person reached age 65 after 1990) to his/her death. […] The NLTCS-M data contain two of the six waves of the NLTCS: namely, the cohorts of years 1994 and 1999. […] In total, 34,077 individuals were followed-up between 1994 and 1999. These individuals were given the detailed NLTCS interview […] which has information on risk factors. More than 200 variables were selected”

In short, these data sets are very large, and contain a lot of information. Here are some results/data:

“Among studied diseases, incidence rates of Alzheimer’s disease, stroke, and heart failure increased with age, while the rates of lung and breast cancers, angina pectoris, diabetes, asthma, emphysema, arthritis, and goiter became lower at advanced ages. [..] Several types of age-patterns of disease incidence could be described. The first was a monotonic increase until age 85–95, with a subsequent slowing down, leveling off, and decline at age 100. This pattern was observed for myocardial infarction, stroke, heart failure, ulcer, and Alzheimer’s disease. The second type had an earlier-age maximum and a more symmetric shape (i.e., an inverted U-shape) which was observed for lung and colon cancers, Parkinson’s disease, and renal failure. The majority of diseases (e.g., prostate cancer, asthma, and diabetes mellitus among them) demonstrated a third shape: a monotonic decline with age or a decline after a short period of increased rates. […] The occurrence of age-patterns with a maximum and, especially, with a monotonic decline contradicts the hypothesis that the risk of geriatric diseases correlates with an accumulation of adverse health events […]. Two processes could be operative in the generation of such shapes. First, they could be attributed to the effect of selection […] when frail individuals do not survive to advanced ages. This approach is popular in cancer modeling […] The second explanation could be related to the possibility of under-diagnosis of certain chronic diseases at advanced ages (due to both less pronounced disease symptoms and infrequent doctor’s office visits); however, that possibility cannot be assessed with the available data […this is because the data sets are based on Medicare claims – US]”

“The most detailed U.S. data on cancer incidence come from the SEER Registry […] about 60 % of malignancies are diagnosed in persons aged 65+ years old […] In the U.S., the estimated percent of cancer patients alive after being diagnosed with cancer (in 2008, by current age) was 13 % for those aged 65–69, 25 % for ages 70–79, and 22 % for ages 80+ years old (compared with 40 % of those aged younger than 65 years old) […] Diabetes affects about 21 % of the U.S. population aged 65+ years old (McDonald et al. 2009). However, while more is known about the prevalence of diabetes, the incidence of this disease among older adults is less studied. […] [In multiple previous studies] the incidence rates of diabetes decreased with age for both males and females. In the present study, we find similar patterns […] The prevalence of asthma among the U.S. population aged 65+ years old in the mid-2000s was as high as 7 % […] older patients are more likely to be underdiagnosed, untreated, and hospitalized due to asthma than individuals younger than age 65 […] asthma incidence rates have been shown to decrease with age […] This trend of declining asthma incidence with age is in agreement with our results.”

“The prevalence and incidence of Alzheimer’s disease increase exponentially with age, with the most notable rise occurring through the seventh and eight decades of life (Reitz et al. 2011). […] whereas dementia incidence continues to increase beyond age 85, the rate of increase slows down [which] suggests that dementia diagnosed at advanced ages might be related not to the aging process per se, but associated with age-related risk factors […] Approximately 1–2 % of the population aged 65+ and up to 3–5 % aged 85+ years old suffer from Parkinson’s disease […] There are few studies of Parkinsons disease incidence, especially in the oldest old, and its age patterns at advanced ages remain controversial”.

“One disadvantage of large administrative databases is that certain factors can produce systematic over/underestimation of the number of diagnosed diseases or of identification of the age at disease onset. One reason for such uncertainties is an incorrect date of disease onset. Other sources are latent disenrollment and the effects of study design. […] the date of onset of a certain chronic disease is a quantity which is not defined as precisely as mortality. This uncertainty makes difficult the construction of a unified definition of the date of onset appropriate for population studies.”

“[W]e investigated the phenomenon of multimorbidity in the U.S. elderly population by analyzing mutual dependence in disease risks, i.e., we calculated disease risks for individuals with specific pre-existing conditions […]. In total, 420 pairs of diseases were analyzed. […] For each pair, we calculated age patterns of unconditional incidence rates of the diseases, conditional rates of the second (later manifested) disease for individuals after onset of the first (earlier manifested) disease, and the hazard ratio of development of the subsequent disease in the presence (or not) of the first disease. […] three groups of interrelations were identified: (i) diseases whose risk became much higher when patients had a certain pre-existing (earlier diagnosed) disease; (ii) diseases whose risk became lower than in the general population when patients had certain pre-existing conditions […] and (iii) diseases for which “two-tail” effects were observed: i.e., when the effects are significant for both orders of disease precedence; both effects can be direct (either one of the diseases from a disease pair increases the risk of the other disease), inverse (either one of the diseases from a disease pair decreases the risk of the other disease), or controversial (one disease increases the risk of the other, but the other disease decreases the risk of the first disease from the disease pair). In general, the majority of disease pairs with increased risk of the later diagnosed disease in both orders of precedence were those in which both the pre-existing and later occurring diseases were cancers, and also when both diseases were of the same organ. […] Generally, the effect of dependence between risks of two diseases diminishes with advancing age. […] Identifying mutual relationships in age-associated disease risks is extremely important since they indicate that development of […] diseases may involve common biological mechanisms.”

“in population cohorts, trends in prevalence result from combinations of trends in incidence, population at risk, recovery, and patients’ survival rates. Trends in the rates for one disease also may depend on trends in concurrent diseases, e.g., increasing survival from CHD contributes to an increase in the cancer incidence rate if the individuals who survived were initially susceptible to both diseases.”

March 1, 2017 Posted by | Biology, Books, Cancer/oncology, Cardiology, Demographics, Diabetes, Epidemiology, Genetics, Medicine, Nephrology, Neurology | Leave a comment

The Ageing Immune System and Health (II)

Here’s the first post about the book. I finished it a while ago but I recently realized I had not completed my intended coverage of the book here on the blog back then, and as some of the book’s material sort-of-kind-of relates to material encountered in a book I’m currently reading (Biodemography of Aging) I decided I might as well finish my coverage of the book now in order to review some things I might have forgot in the meantime, by providing coverage here of some of the material covered in the second half of the book. It’s a nice book with some interesting observations, but as I also pointed out in my first post it is definitely not an easy read. Below I have included some observations from the book’s second half.

Lungs:

“The aged lung is characterised by airspace enlargement similar to, but not identical with acquired emphysema [4]. Such tissue damage is detected even in non-smokers above 50 years of age as the septa of the lung alveoli are destroyed and the enlarged alveolar structures result in a decreased surface for gas exchange […] Additional problems are that surfactant production decreases with age [6] increasing the effort needed to expand the lungs during inhalation in the already reduced thoracic cavity volume where the weakened muscles are unable to thoroughly ventilate. […] As ageing is associated with respiratory muscle strength reduction, coughing becomes difficult making it progressively challenging to eliminate inhaled particles, pollens, microbes, etc. Additionally, ciliary beat frequency (CBF) slows down with age impairing the lungs’ first line of defence: mucociliary clearance [9] as the cilia can no longer repel invading microorganisms and particles. Consequently e.g. bacteria can more easily colonise the airways leading to infections that are frequent in the pulmonary tract of the older adult.”

“With age there are dramatic changes in neutrophil function, including reduced chemotaxis, phagocytosis and bactericidal mechanisms […] reduced bactericidal function will predispose to infection but the reduced chemotaxis also has consequences for lung tissue as this results in increased tissue bystander damage from neutrophil elastases released during migration […] It is currently accepted that alterations in pulmonary PPAR profile, more precisely loss of PPARγ activity, can lead to inflammation, allergy, asthma, COPD, emphysema, fibrosis, and cancer […]. Since it has been reported that PPARγ activity decreases with age, this provides a possible explanation for the increasing incidence of these lung diseases and conditions in older individuals [6].”

Cancer:

“Age is an important risk factor for cancer and subjects aged over 60 also have a higher risk of comorbidities. Approximately 50 % of neoplasms occur in patients older than 70 years […] a major concern for poor prognosis is with cancer patients over 70–75 years. These patients have a lower functional reserve, a higher risk of toxicity after chemotherapy, and an increased risk of infection and renal complications that lead to a poor quality of life. […] [Whereas] there is a difference in organs with higher cancer incidence in developed versus developing countries [,] incidence increases with ageing almost irrespective of country […] The findings from Surveillance, Epidemiology and End Results Program [SEERincidentally I likely shall at some point discuss this one in much more detail, as the aforementioned biodemography textbook covers this data in a lot of detail.. – US] [6] show that almost a third of all cancer are diagnosed after the age of 75 years and 70 % of cancer-related deaths occur after the age of 65 years. […] The traditional clinical trial focus is on younger and healthier patient, i.e. with few or no co-morbidities. These restrictions have resulted in a lack of data about the optimal treatment for older patients [7] and a poor evidence base for therapeutic decisions. […] In the older patient, neutropenia, anemia, mucositis, cardiomyopathy and neuropathy — the toxic effects of chemotherapy — are more pronounced […] The correction of comorbidities and malnutrition can lead to greater safety in the prescription of chemotherapy […] Immunosenescence is a general classification for changes occurring in the immune system during the ageing process, as the distribution and function of cells involved in innate and adaptive immunity are impaired or remodelled […] Immunosenescence is considered a major contributor to cancer development in aged individuals“.

Neurodegenerative diseases:

“Dementia and age-related vision loss are major causes of disability in our ageing population and it is estimated that a third of people aged over 75 are affected. […] age is the largest risk factor for the development of neurodegenerative diseases […] older patients with comorbidities such as atherosclerosis, type II diabetes or those suffering from repeated or chronic systemic bacterial and viral infections show earlier onset and progression of clinical symptoms […] analysis of post-mortem brain tissue from healthy older individuals has provided evidence that the presence of misfolded proteins alone does not correlate with cognitive decline and dementia, implying that additional factors are critical for neural dysfunction. We now know that innate immune genes and life-style contribute to the onset and progression of age-related neuronal dysfunction, suggesting that chronic activation of the immune system plays a key role in the underlying mechanisms that lead to irreversible tissue damage in the CNS. […] Collectively these studies provide evidence for a critical role of inflammation in the pathogenesis of a range of neurodegenerative diseases, but the factors that drive or initiate inflammation remain largely elusive.”

“The effect of infection, mimicked experimentally by administration of bacterial lipopolysaccharide (LPS) has revealed that immune to brain communication is a critical component of a host organism’s response to infection and a collection of behavioural and metabolic adaptations are initiated over the course of the infection with the purpose of restricting the spread of a pathogen, optimising conditions for a successful immune response and preventing the spread of infection to other organisms [10]. These behaviours are mediated by an innate immune response and have been termed ‘sickness behaviours’ and include depression, reduced appetite, anhedonia, social withdrawal, reduced locomotor activity, hyperalgesia, reduced motivation, cognitive impairment and reduced memory encoding and recall […]. Metabolic adaptation to infection include fever, altered dietary intake and reduction in the bioavailability of nutrients that may facilitate the growth of a pathogen such as iron and zinc [10]. These behavioural and metabolic adaptions are evolutionary highly conserved and also occur in humans”.

“Sickness behaviour and transient microglial activation are beneficial for individuals with a normal, healthy CNS, but in the ageing or diseased brain the response to peripheral infection can be detrimental and increases the rate of cognitive decline. Aged rodents exhibit exaggerated sickness and prolonged neuroinflammation in response to systemic infection […] Older people who contract a bacterial or viral infection or experience trauma postoperatively, also show exaggerated neuroinflammatory responses and are prone to develop delirium, a condition which results in a severe short term cognitive decline and a long term decline in brain function […] Collectively these studies demonstrate that peripheral inflammation can increase the accumulation of two neuropathological hallmarks of AD, further strengthening the hypothesis that inflammation i[s] involved in the underlying pathology. […] Studies from our own laboratory have shown that AD patients with mild cognitive impairment show a fivefold increased rate of cognitive decline when contracting a systemic urinary tract or respiratory tract infection […] Apart from bacterial infection, chronic viral infections have also been linked to increased incidence of neurodegeneration, including cytomegalovirus (CMV). This virus is ubiquitously distributed in the human population, and along with other age-related diseases such as cardiovascular disease and cancer, has been associated with increased risk of developing vascular dementia and AD [66, 67].”

Frailty:

“Frailty is associated with changes to the immune system, importantly the presence of a pro-inflammatory environment and changes to both the innate and adaptive immune system. Some of these changes have been demonstrated to be present before the clinical features of frailty are apparent suggesting the presence of potentially modifiable mechanistic pathways. To date, exercise programme interventions have shown promise in the reversal of frailty and related physical characteristics, but there is no current evidence for successful pharmacological intervention in frailty. […] In practice, acute illness in a frail person results in a disproportionate change in a frail person’s functional ability when faced with a relatively minor physiological stressor, associated with a prolonged recovery time […] Specialist hospital services such as surgery [15], hip fractures [16] and oncology [17] have now begun to recognise frailty as an important predictor of mortality and morbidity.

I should probably mention here that this is another area where there’s an overlap between this book and the biodemography text I’m currently reading; chapter 7 of the latter text is about ‘Indices of Cumulative Deficits’ and covers this kind of stuff in a lot more detail than does this one, including e.g. detailed coverage of relevant statistical properties of one such index. Anyway, back to the coverage:

“Population based studies have demonstrated that the incidence of infection and subsequent mortality is higher in populations of frail people. […] The prevalence of pneumonia in a nursing home population is 30 times higher than the general population [39, 40]. […] The limited data available demonstrates that frailty is associated with a state of chronic inflammation. There is also evidence that inflammageing predates a diagnosis of frailty suggesting a causative role. […] A small number of studies have demonstrated a dysregulation of the innate immune system in frailty. Frail adults have raised white cell and neutrophil count. […] High white cell count can predict frailty at a ten year follow up [70]. […] A recent meta-analysis and four individual systematic reviews have found beneficial evidence of exercise programmes on selected physical and functional ability […] exercise interventions may have no positive effect in operationally defined frail individuals. […] To date there is no clear evidence that pharmacological interventions improve or ameliorate frailty.”

Exercise:

“[A]s we get older the time and intensity at which we exercise is severely reduced. Physical inactivity now accounts for a considerable proportion of age-related disease and mortality. […] Regular exercise has been shown to improve neutrophil microbicidal functions which reduce the risk of infectious disease. Exercise participation is also associated with increased immune cell telomere length, and may be related to improved vaccine responses. The anti-inflammatory effect of regular exercise and negative energy balance is evident by reduced inflammatory immune cell signatures and lower inflammatory cytokine concentrations. […] Reduced physical activity is associated with a positive energy balance leading to increased adiposity and subsequently systemic inflammation [5]. […] Elevated neutrophil counts accompany increased inflammation with age and the increased ratio of neutrophils to lymphocytes is associated with many age-related diseases including cancer [7]. Compared to more active individuals, less active and overweight individuals have higher circulating neutrophil counts [8]. […] little is known about the intensity, duration and type of exercise which can provide benefits to neutrophil function. […] it remains unclear whether exercise and physical activity can override the effects of NK cell dysfunction in the old. […] A considerable number of studies have assessed the effects of acute and chronic exercise on measures of T-cell immunesenescence including T cell subsets, phenotype, proliferation, cytokine production, chemotaxis, and co-stimulatory capacity. […] Taken together exercise appears to promote an anti-inflammatory response which is mediated by altered adipocyte function and improved energy metabolism leading to suppression of pro-inflammatory cytokine production in immune cells.”

February 24, 2017 Posted by | Biology, Books, Cancer/oncology, Epidemiology, Immunology, Medicine, Neurology | Leave a comment

Diabetes and the Brain (III)

Some quotes from the book below.

Tests that are used in clinical neuropsychology in most cases examine one or more aspects of cognitive domains, which are theoretical constructs in which a multitude of cognitive processes are involved. […] By definition, a subdivision in cognitive domains is arbitrary, and many different classifications exist. […] for a test to be recommended, several criteria must be met. First, a test must have adequate reliability: the test must yield similar outcomes when applied over multiple test sessions, i.e., have good test–retest reliability. […] Furthermore, the interobserver reliability is important, in that the test must have a standardized assessment procedure and is scored in the same manner by different examiners. Second, the test must have adequate validity. Here, different forms of validity are important. Content validity is established by expert raters with respect to item formulation, item selection, etc. Construct validity refers to the underlying theoretical construct that the test is assumed to measure. To assess construct validity, both convergent and divergent validities are important. Convergent validity refers to the amount of agreement between a given test and other tests that measure the same function. In turn, a test with a good divergent validity correlates minimally with tests that measure other cognitive functions. Moreover, predictive validity (or criterion validity) is related to the degree of correlation between the test score and an external criterion, for example, the correlation between a cognitive test and functional status. […] it should be stressed that cognitive tests alone cannot be used as ultimate proof for organic brain damage, but should be used in combination with more direct measures of cerebral abnormalities, such as neuroimaging.”

“Intelligence is a theoretically ill-defined construct. In general, it refers to the ability to think in an abstract manner and solve new problems. Typically, two forms of intelligence are distinguished, crystallized intelligence (academic skills and knowledge that one has acquired during schooling) and fluid intelligence (the ability to solve new problems). Crystallized intelligence is better preserved in patients with brain disease than fluid intelligence (3). […] From a neuropsychological viewpoint, the concept of intelligence as a unitary construct (often referred to as g-factor) does not provide valuable information, since deficits in specific cognitive functions may be averaged out in the total IQ score. Thus, in most neuropsychological studies, intelligence tests are included because of specific subtests that are assumed to measure specific cognitive functions, and the performance profile is analyzed rather than considering the IQ measure as a compound score in isolation.”

“Attention is a concept that in general relates to the selection of relevant information from our environment and the suppression of irrelevant information (selective or “focused” attention), the ability to shift attention between tasks (divided attention), and to maintain a state of alertness to incoming stimuli over longer periods of time (concentration and vigilance). Many different structures in the human brain are involved in attentional processing and, consequently, disorders in attention occur frequently after brain disease or damage (21). […] Speed of information processing is not a localized cognitive function, but depends greatly on the integrity of the cerebral network as a whole, the subcortical white matter and the interhemispheric and intrahemispheric connections. It is one of the cognitive functions that clearly declines with age and it is highly susceptible to brain disease or dysfunction of any kind.”

“The MiniMental State Examination (MMSE) is a screening instrument that has been developed to determine whether older adults have cognitive impairments […] numerous studies have shown that the MMSE has poor sensitivity and specificity, as well as a low-test–retest reliability […] the MMSE has been developed to determine cognitive decline that is typical for Alzheimer’s dementia, but has been found less useful in determining cognitive decline in nondemented patients (44) or in patients with other forms of dementia. This is important since odds ratios for both vascular dementia and Alzheimer’s dementia are increased in diabetes (45). Notwithstanding this increased risk, most patients with diabetes have subtle cognitive deficits (46, 47) that may easily go undetected using gross screening instruments such as the MMSE. For research in diabetes a high sensitivity is thus especially important. […] ceiling effects in test performance often result in a lack of sensitivity. Subtle impairments are easily missed, resulting in a high proportion of false-negative cases […] In general, tests should be cognitively demanding to avoid ceiling effects in patients with mild cognitive dysfunction.[…] sensitive domains such as speed of information processing, (working) memory, attention, and executive function should be examined thoroughly in diabetes patients, whereas other domains such as language, motor function, and perception are less likely to be affected. Intelligence should always be taken into account, and confounding factors such as mood, emotional distress, and coping are crucial for the interpretation of the neuropsychological test results.”

“The life-time risk of any dementia has been estimated to be more than 1 in 5 for women and 1 in 6 for men (2). Worldwide, about 24 million people have dementia, with 4.6 million new cases of dementia every year (3). […] Dementia can be caused by various underlying diseases, the most common of which is Alzheimer’s disease (AD) accounting for roughly 70% of cases in the elderly. The second most common cause of dementia is vascular dementia (VaD), accounting for 16% of cases. Other, less common, causes include dementia with Lewy bodies (DLB) and frontotemporal lobar degeneration (FTLD). […] It is estimated that both the incidence and the prevalence [of AD] double with every 5-year increase in age. Other risk factors for AD include female sex and vascular risk factors, such as diabetes, hypercholesterolaemia and hypertension […] In contrast with AD, progression of cognitive deficits [in VaD] is mostly stepwise and with an acute or subacute onset. […] it is clear that cerebrovascular disease is one of the major causes of cognitive decline. Vascular risk factors such as diabetes mellitus and hypertension have been recognized as risk factors for VaD […] Although pure vascular dementia is rare, cerebrovascular pathology is frequently observed on MRI and in pathological studies of patients clinically diagnosed with AD […] Evidence exists that AD and cerebrovascular pathology act synergistically (60).”

“In type 1 diabetes the annual prevalence of severe hypoglycemia (requiring help for recovery) is 30–40% while the annual incidence varies depending on the duration of diabetes. In insulin-treated type 2 diabetes, the frequency is lower but increases with duration of insulin therapy. […] In normal health, blood glucose is maintained within a very narrow range […] The functioning of the brain is optimal within this range; cognitive function rapidly becomes impaired when the blood glucose falls below 3.0 mmol/l (54 mg/dl) (3). Similarly, but much less dramatically, cognitive function deteriorates when the brain is exposed to high glucose concentrations” (I did not know the latter for certain, but I certainly have had my suspicions for a long time).

“When exogenous insulin is injected into a non-diabetic adult human, peripheral tissues such as skeletal muscle and adipose tissue rapidly take up glucose, while hepatic glucose output is suppressed. This causes blood glucose to fall and triggers a series of counterregulatory events to counteract the actions of insulin; this prevents a progressive decline in blood glucose and subsequently reverses the hypoglycemia. In people with insulin-treated diabetes, many of the homeostatic mechanisms that regulate blood glucose are either absent or deficient. [If you’re looking for more details on these topics, it should perhaps be noted here that Philip Cryer’s book on these topics is very nice and informative]. […] The initial endocrine response to a fall in blood glucose in non-diabetic humans is the suppression of endogenous insulin secretion. This is followed by the secretion of the principal counterregulatory hormones, glucagon and epinephrine (adrenaline) (5). Cortisol and growth hormone also contribute, but have greater importance in promoting recovery during exposure to prolonged hypoglycemia […] Activation of the peripheral sympathetic nervous system and the adrenal glands provokes the release of a copious quantity of catecholamines, epinephrine, and norepinephrine […] Glucagon is secreted from the alpha cells of the pancreatic islets, apparently in response to localized neuroglycopenia and independent of central neural control. […] The large amounts of catecholamines that are secreted in response to hypoglycemia exert other powerful physiological effects that are unrelated to counterregulation. These include major hemodynamic actions with direct effects on the heart and blood pressure. […] regional blood flow changes occur during hypoglycemia that encourages the transport of substrates to the liver for gluconeogenesis and simultaneously of glucose to the brain. Organs that have no role in the response to acute stress, such as the spleen and kidneys, are temporarily under-perfused. The mobilisation and activation of white blood cells are accompanied by hemorheological effects, promoting increased viscosity, coagulation, and fibrinolysis and may influence endothelial function (6). In normal health these acute physiological changes probably exert no harmful effects, but may acquire pathological significance in people with diabetes of long duration.”

“The more complex and attention-demanding cognitive tasks, and those that require speeded responses are more affected by hypoglycemia than simple tasks or those that do not require any time restraint (3). The overall speed of response of the brain in making decisions is slowed, yet for many tasks, accuracy is preserved at the expense of speed (8, 9). Many aspects of mental performance become impaired when blood glucose falls below 3.0 mmol/l […] Recovery of cognitive function does not occur immediately after the blood glucose returns to normal, but in some cognitive domains may be delayed for 60 min or more (3), which is of practical importance to the performance of tasks that require complex cognitive functions, such as driving. […] [the] major changes that occur during hypoglycemia – counterregulatory hormone secretion, symptom generation, and cognitive dysfunction – occur as components of a hierarchy of responses, each being triggered as the blood glucose falls to its glycemic threshold. […] In nondiabetic individuals, the glycemic thresholds are fixed and reproducible (10), but in people with diabetes, these thresholds are dynamic and plastic, and can be modified by external factors such as glycemic control or exposure to preceding (antecedent) hypoglycemia (11). Changes in the glycemic thresholds for the responses to hypoglycemia underlie the effects of the acquired hypoglycemia syndromes that can develop in people with insulin-treated diabetes […] the incidence of severe hypoglycemia in people with insulin-treated type 2 diabetes increases steadily with duration of insulin therapy […], as pancreatic beta-cell failure develops. The under-recognized risk of severe hypoglycemia in insulin-treated type 2 diabetes is of great practical importance as this group is numerically much larger than people with type 1 diabetes and encompasses many older, and some very elderly, people who may be exposed to much greater danger because they often have co-morbidities such as macrovascular disease, osteoporosis, and general frailty.”

“Hypoglycemia occurs when a mismatch develops between the plasma concentrations of glucose and insulin, particularly when the latter is inappropriately high, which is common during the night. Hypoglycemia can result when too much insulin is injected relative to oral intake of carbohydrate or when a meal is missed or delayed after insulin has been administered. Strenuous exercise can precipitate hypoglycemia through accelerated absorption of insulin and depletion of muscle glycogen stores. Alcohol enhances the risk of prolonged hypoglycemia by inhibiting hepatic gluconeogenesis, but the hypoglycemia may be delayed for several hours. Errors of dosage or timing of insulin administration are common, and there are few conditions where the efficacy of the treatment can be influenced by so many extraneous factors. The time–action profiles of different insulins can be modified by factors such as the ambient temperature or the site and depth of injection and the person with diabetes has to constantly try to balance insulin requirement with diet and exercise. It is therefore not surprising that hypoglycemia occurs so frequently. […] The lower the median blood glucose during the day, the greater the frequency
of symptomatic and biochemical hypoglycemia […] Strict glycemic control can […] induce the acquired hypoglycemia syndromes, impaired awareness of hypoglycemia (a major risk factor for severe hypoglycemia), and counterregulatory hormonal deficiencies (which interfere with blood glucose recovery). […] Severe hypoglycemia is more common at the extremes of age – in very young children and in elderly people.
[…] In type 1 diabetes the frequency of severe hypoglycemia increases with duration of diabetes (12), while in type 2 diabetes it is associated with increasing duration of insulin treatment (18). […] Around one quarter of all episodes of severe hypoglycemia result in coma […] In 10% of episodes of severe hypoglycemia affecting people with type 1 diabetes and around 30% of those in people with insulin-treated type 2 diabetes, the assistance of the emergency medical services is required (23). However, most episodes (both mild and severe) are treated in the community, and few people require admission to hospital.”

“Severe hypoglycemia is potentially dangerous and has a significant mortality and morbidity, particularly in older people with insulin-treated diabetes who often have premature macrovascular disease. The hemodynamic effects of autonomic stimulation may provoke acute vascular events such as myocardial ischemia and infarction, cardiac failure, cerebral ischemia, and stroke (6). In clinical practice the cardiovascular and cerebrovascular consequences of hypoglycemia are frequently overlooked because the role of hypoglycemia in precipitating the vascular event is missed. […] The profuse secretion of catecholamines in response to hypoglycemia provokes a fall in plasma potassium and causes electrocardiographic (ECG) changes, which in some individuals may provoke a cardiac arrhythmia […]. A possible mechanism that has been observed with ECG recordings during hypoglycemia is prolongation of the QT interval […]. Hypoglycemia-induced arrhythmias during sleep have been implicated as the cause of the “dead in bed” syndrome that is recognized in young people with type 1 diabetes (40). […] Total cerebral blood flow is increased during acute hypoglycemia while regional blood flow within the brain is altered acutely. Blood flow increases in the frontal cortex, presumably as a protective compensatory mechanism to enhance the supply of available glucose to the most vulnerable part of the brain. These regional vascular changes become permanent in people who are exposed to recurrent severe hypoglycemia and in those with impaired awareness of hypoglycemia, and are then present during normoglycemia (41). This probably represents an adaptive response of the brain to recurrent exposure to neuroglycopenia. However, these permanent hypoglycemia-induced changes in regional cerebral blood flow may encourage localized neuronal ischemia, particularly if the cerebral circulation is already compromised by the development of cerebrovascular disease associated with diabetes. […] Hypoglycemia-induced EEG changes can persist for days or become permanent, particularly after recurrent severe hypoglycemia”.

“In the large British Diabetic Association Cohort Study of people who had developed type 1 diabetes before the age of 30, acute metabolic complications of diabetes were the greatest single cause of excess death under the age of 30; hypoglycemia was the cause of death in 18% of males and 6% of females in the 20–49 age group (47).”

“[The] syndromes of counterregulatory hormonal deficiencies and impaired awareness of hypoglycemia (IAH) develop over a period of years and ultimately affect a substantial proportion of people with type 1 diabetes and a lesser number with insulin-treated type 2 diabetes. They are considered to be components of hypoglycemia-associated autonomic failure (HAAF), through down-regulation of the central mechanisms within the brain that would normally activate glucoregulatory responses to hypoglycemia, including the release of counterregulatory hormones and the generation of warning symptoms (48). […] The glucagon secretory response to hypoglycemia becomes diminished or absent within a few years of the onset of insulin-deficient diabetes. With glucagon deficiency alone, blood glucose recovery from hypoglycemia is not noticeably affected because the secretion of epinephrine maintains counterregulation. However, almost half of those who have type 1 diabetes of 20 years duration have evidence of impairment of both glucagon and epinephrine in response to hypoglycemia (49); this seriously delays blood glucose recovery and allows progression to more severe and prolonged hypoglycemia when exposed to low blood glucose. People with type 1 diabetes who have these combined counterregulatory hormonal deficiencies have a 25-fold higher risk of experiencing severe hypoglycemia if they are subjected to intensive insulin therapy compared with those who have lost their glucagon response but have retained epinephrine secretion […] Impaired awareness is not an “all or none” phenomenon. “Partial” impairment of awareness may develop, with the individual being aware of some episodes of hypoglycemia but not others (53). Alternatively, the intensity or number of symptoms may be reduced, and neuroglycopenic symptoms predominate. […] total absence of any symptoms, albeit subtle, is very uncommon […] IAH affects 20–25% of patients with type 1 diabetes (11, 55) and less than 10% with type 2 diabetes (24), becomes more prevalent with increasing duration of diabetes (12) […], and predisposes the patient to a sixfold higher risk of severe hypoglycemia than people who retain normal awareness (56). When IAH is associated with strict glycemic control during intensive insulin therapy or has followed episodes of recurrent severe hypoglycemia, it may be reversible by relaxing glycemic control or by avoiding further hypoglycemia (11), but in many patients with type 1 diabetes of long duration, it appears to be a permanent defect. […] The modern management of diabetes strives to achieve strict glycemic control using intensive therapy to avoid or minimize the long-term complications of diabetes; this strategy tends to increase the risk of hypoglycemia and promotes development of the acquired hypoglycemia syndromes.”

February 5, 2017 Posted by | Books, Cardiology, Diabetes, Epidemiology, Medicine, Neurology, Psychology | Leave a comment

Diabetes and the Brain (II)

Here’s my first post about the book, which I recently finished – here’s my goodreads review. I added the book to my list of favourite books on goodreads, it’s a great textbook. Below some observations from the first few chapters of the book.

“Several studies report T1D [type 1 diabetes] incidence numbers of 0.1–36.8/100,000 subjects worldwide (2). Above the age of 15 years ketoacidosis at presentation occurs on average in 10% of the population; in children ketoacidosis at presentation is more frequent (3, 4). Overall, publications report a male predominance (1.8 male/female ratio) and a seasonal pattern with higher incidence in November through March in European countries. Worldwide, the incidence of T1D is higher in more developed countries […] After asthma, T1D is a leading cause of chronic disease in children. […]  twin studies show a low concordant prevalence of T1D of only 30–55%. […] Diabetes mellitus type 1 may be sporadic or associated with other autoimmune diseases […] The latter has been classified as autoimmune polyglandular syndrome type II (APS-II). APS-II is a polygenic disorder with a female preponderance which typically occurs between the ages of 20 and 40 years […] In clinical practice, anti-thyroxine peroxidase (TPO) positive hypothyroidism is the most frequent concomitant autoimmune disease in type 1 diabetic patients, therefore all type 1 diabetic patients should annually be screened for the presence of anti-TPO antibodies. Other frequently associated disorders are atrophic gastritis leading to vitamin B12 deficiency (pernicious anemia) and vitiligo. […] The normal human pancreas contains a superfluous amount of β-cells. In T1D, β-cell destruction therefore remains asymptomatic until a critical β-cell reserve is left. This destructive process takes months to years […] Only in a minority of type 1 diabetic patients does the disease begin with diabetic ketoacidosis, the majority presents with a milder course that may be mistaken as type 2 diabetes (7).”

“Insulin is the main regulator of glucose metabolism by stimulating glucose uptake in tissues and glycogen storage in liver and muscle and by inhibiting gluconeogenesis in the liver (11). Moreover, insulin is a growth factor for cells and cell differentiation, and acting as anabolic hormone insulin stimulates lipogenesis and protein synthesis. Glucagon is the counterpart of insulin and is secreted by the α-cells in the pancreatic islets in an inversely proportional quantity to the insulin concentration. Glucagon, being a catabolic hormone, stimulates glycolysis and gluconeogenesis in the liver as well as lipolysis and uptake of amino acids in the liver. Epinephrine and norepinephrine have comparable catabolic effects […] T1D patients lose the glucagon response to hypoglycemia after several years, when all β-cells are destructed […] The risk of hypoglycemia increases with improved glycemic control, autonomic neuropathy, longer duration of diabetes, and the presence of long-term complications (17) […] Long-term complications are prevalent in any population of type 1 diabetic patients with increasing prevalence and severity in relation to disease duration […] The pathogenesis of diabetic complications is multifactorial, complicated, and not yet fully elucidated.”

“Cataract is much more frequent in patients with diabetes and tends to become clinically significant at a younger age. Glaucoma is markedly increased in diabetes too.” (I was unaware of this).

“T1D should be considered as an independent risk factor for atherosclerosis […] An older study shows that the cumulative mortality of coronary heart disease in T1D was 35% by the age 55 (34). In comparison, the Framingham Heart Study showed a cardiovascular mortality of 8% of men and 4% of women without diabetes, respectively. […] Atherosclerosis is basically a systemic disease. Patients with one clinically apparent localization are at risk for other manifestations. […] Musculoskeletal disease in diabetes is best viewed as a systemic disorder with involvement of connective tissue. Potential pathophysiological mechanisms that play a role are glycosylation of collagen, abnormal cross-linking of collagen, and increased collagen hydration […] Dupuytren’s disease […] may be observed in up to 42% of adults with diabetes mellitus, typically in patients with long-standing T1D. Dupuytren’s is characterized by thickening of the palmar fascia due to fibrosis with nodule formation and contracture, leading to flexion contractures of the digits, most commonly affecting the fourth and fifth digits. […] Foot problems in diabetes are common and comprise ulceration, infection, and gangrene […] The lifetime risk of a foot ulcer for diabetic patients is about 15% (42). […] Wound depth is an important determinant of outcome (46, 47). Deep ulcers with cellulitis or abscess formation often involve osteomyelitis. […] Radiologic changes occur late in the course of osteomyelitis and negative radiographs certainly do not exclude it.”

“Education of people with diabetes is a comprehensive task and involves teamwork by a team that comprises at least a nurse educator, a dietician, and a physician. It is, however, essential that individuals with diabetes assume an active role in their care themselves, since appropriate self-care behavior is the cornerstone of the treatment of diabetes.” (for much more on these topics, see Simmons et al.)

“The International Diabetes Federation estimates that more than 245 million people around the world have diabetes (4). This total is expected to rise to 380 million within 20 years. Each year a further 7 million people develop diabetes. Diabetes, mostly type 2 diabetes (T2D), now affects 5.9% of the world’s adult population with almost 80% of the total in developing countries. […] According to […] 2007 prevalence data […] [a]lmost 25% of the population aged 60 years and older had diabetes in 2007. […] It has been projected that one in three Americans born in 2000 will develop diabetes, with the highest estimated lifetime risk among Latinos (males, 45.4% and females, 52.5%) (6). A rise in obesity rates is to blame for much of the increase in T2D (7). Nearly two-thirds of American adults are overweight or obese (8). [my bold, US]

“In the natural history of progression to diabetes, β-cells initially increase insulin secretion in response to insulin resistance and, for a period of time, are able to effectively maintain glucose levels below the diabetic range. However, when β-cell function begins to decline, insulin production is inadequate to overcome the insulin resistance, and blood glucose levels rise. […] Insulin resistance, once established, remains relatively stable over time. […] progression of T2D is a result of worsening β-cell function with pre-existing insulin resistance.”

“Lifestyle modification (i.e., weight loss through diet and increased physical activity) has proven effective in reducing incident T2D in high-risk groups. The Da Qing Study (China) randomly allocated 33 clinics (557 persons with IGT) to 1 of 4 study conditions: control, diet, exercise, or diet plus exercise (23). Compared with the control group, the incidence of diabetes was reduced in the three intervention groups by 31, 46, and 42%, respectively […] The Finnish Diabetes Prevention Study evaluated 522 obese persons with IGT randomly allocated on an individual basis to a control group or a lifestyle intervention group […] During the trial, the incidence of diabetes was reduced by 58% in the lifestyle group compared with the control group. The US Diabetes Prevention Program is the largest trial of primary prevention of diabetes to date and was conducted at 27 clinical centers with 3,234 overweight and obese participants with IGT randomly allocated to 1 of 3 study conditions: control, use of metformin, or intensive lifestyle intervention […] Over 3 years, the incidence of diabetes was reduced by 31% in the metformin group and by 58% in the lifestyle group; the latter value is identical to that observed in the Finnish Study. […] Metformin is recommended as first choice for pharmacologic treatment [of type 2 diabetes] and has good efficacy to lower HbA1c […] However, most patients will eventually require treatment with combinations of oral medications with different mechanisms of action simultaneously in order to attain adequate glycemic control.”

CVD [cardiovascular disease, US] is the cause of 65% of deaths in patients with T2D (31). Epidemiologic studies have shown that the risk of a myocardial infarction (MI) or CVD death in a diabetic individual with no prior history of CVD is comparable to that of an individual who has had a previous MI (32, 33). […] Stroke is the second leading cause of long-term disability in high-income countries and the second leading cause of death worldwide. […] Stroke incidence is highly age-dependent. The median stroke incidence in persons between 15 and 49 years of age is 10 per 100,000 per year, whereas this is 2,000 per 100,000 for persons aged 85 years or older. […] In Western communities, about 80% of strokes are caused by focal cerebral ischemia, secondary to arterial occlusion, 15% by intracerebral hemorrhage, and 5% by subarachnoid hemorrhage (2). […] Patients with ischemic stroke usually present with focal neurological deficit of sudden onset. […] Common deficits include dysphasia, dysarthria, hemianopia, weakness, ataxia, sensory loss, and cognitive disorders such as spatial neglect […] Mild-to-moderate headache is an accompanying symptom in about a quarter of all patients with ischemic stroke […] The risk of symptomatic intracranial hemorrhage after thrombolysis is higher with more severe strokes and higher age (21). [worth keeping in mind when in the ‘I-am-angry-and-need-someone-to-blame-for-the-death-of-individual-X-phase’ – if the individual died as a result of the treatment, the prognosis was probably never very good to start with..] […] Thirty-day case fatality rates for ischemic stroke in Western communities generally range between 10 and 17% (2). Stroke outcome strongly depends not only on age and comorbidity, but also on the type and cause of the infarct. Early case fatality can be as low as 2.5% in patients with lacunar infarcts (7) and as high as 78% in patients with space-occupying hemispheric infarction (8).”

“In the previous 20 years, ten thousands of patients with acute ischemic stroke have participated in hundreds of clinical trials of putative neuroprotective therapies. Despite this enormous effort, there is no evidence of benefit of a single neuroprotective agent in humans, whereas over 500 have been effective in animal models […] the failure of neuroprotective agents in the clinic may […] be explained by the fact that most neuroprotectants inhibit only a single step in the broad cascade of events that lead to cell death (9). Currently, there is no rationale for the use of any neuroprotective medication in patients with acute ischemic stroke.”

“Between 5 and 10% of patients with ischemic stroke suffer from epileptic seizures in the first week and about 3% within the first 24 h […] Post-stroke seizures are not associated with a higher mortality […] About 1 out of every 11 patient with an early epileptic seizure develops epilepsy within 10 years after stroke onset (51) […] In the first 12 h after stroke onset, plasma glucose concentrations are elevated in up to 68% of patients, of whom more than half are not known to have diabetes mellitus (53). An initially high blood glucose concentration in patients with acute stroke is a predictor of poor outcome (53, 54). […] Acute stroke is associated with a blood pressure higher than 170/110 mmHg in about two thirds of patients. Blood pressure falls spontaneously in the majority of patients during the first week after stroke. High blood pressure during the acute phase of stroke has been associated with a poor outcome (56). It is unclear how blood pressure should be managed during the acute phase of ischemic stroke. […] routine lowering of the blood pressure is not recommended in the first week after stroke, except for extremely elevated values on repeated measurements […] Urinary incontinence affects up to 60% of stroke patients admitted to hospital, with 25% still having problems on hospital discharge, and around 15% remaining incontinent at 1 year. […] Between 22 and 43% of patients develop fever or subfebrile temperatures during the first days after stroke […] High body temperature in the first days after stroke is associated with poor outcome (42, 67). There is currently no evidence from randomized trials to support the routine lowering of body temperature above 37◦C.”

December 28, 2016 Posted by | Books, Cardiology, Diabetes, Epidemiology, Immunology, Medicine, Neurology | Leave a comment

Diabetes and the brain (I)

I recently learned that the probability that I have brain-damage as a result of my diabetes is higher than I thought it was.

I first took note of the fact that there might be a link between diabetes and brain development some years ago, but this is a topic I knew very little about before reading the book I’m currently reading. Below I have added some relevant quotes from chapters 10 and 11 of the book:

“Cognitive decrements [in adults with type 1 diabetes] are limited to only some cognitive domains and can best be characterised as a slowing of mental speed and a diminished mental flexibility, whereas learning and memory are generally spared. […] the cognitive decrements are mild in magnitude […] and seem neither to be progressive over time, nor to be substantially worse in older adults. […] neuroimaging studies […] suggest that type 1 diabetic patients have relatively subtle reductions in brain volume but these structural changes may be more pronounced in patients with an early disease onset.”

“With the rise of the subspecialty area ‘medical neuropsychology’ […] it has become apparent that many medical conditions may […] affect the structure and function of the central nervous system (CNS). Diabetes mellitus has received much attention in that regard, and there is now an extensive literature demonstrating that adults with type 1 diabetes have an elevated risk of CNS anomalies. This literature is no longer limited to small cross-sectional studies in relatively selected populations of young adults with type 1 diabetes, but now includes studies that investigated the pattern and magnitude of neuropsychological decrements and the associated neuroradiological changes in much more detail, with more sensitive measurements, in both younger and older patients.”

“Compared to non-diabetic controls, the type 1 diabetic group [in a meta-analysis including 33 studies] demonstrated a significant overall lowered performance, as well as impairment in the cognitive domains intelligence, implicit memory, speed of information processing, psychomotor efficiency, visual and sustained attention, cognitive flexibility, and visual perception. There was no difference in explicit memory, motor speed, selective attention, or language function. […] These results strongly support the hypothesis that there is a relationship between cognitive dysfunction and type 1 diabetes. Clearly, there is a modest, but statistically significant, lowered cognitive performance in patients with type 1 diabetes compared to non-diabetic controls. The pattern of cognitive findings does not suggest decline in all cognitive domains, but is characterised by a slowing of mental speed and a diminished mental flexibility. Patients with type 1 diabetes seem to be less able to flexibly apply acquired knowledge in a new situation. […] In all, the cognitive problems we see in type 1 diabetes mimics the patterns of cognitive ageing. […] One of the problems with much of this research is that it is conducted in patients who are seen in specialised medical centres where care is very good. Other aspects of population selection may also have affected the results. Persons who participate in research projects that include a detailed work-up at a hospital tend to be less affected than persons who refuse participation. Possibly, specific studies that recruit type 1 adults from the community, with individuals being in poorer health, would result in greater cognitive deficits”.

“[N]eurocognitive research suggests that type 1 diabetes is primarily associated with psychomotor slowing and reductions in mental efficiency. This pattern is more consistent with damage to the brain’s white matter than with grey-matter abnormalities. […] A very large neuroimaging literature indicates that adults with either type 1 or type 2 diabetes manifest structural changes in a number of brain regions […]. MRI changes in the brain of patients with type 1 diabetes are relatively subtle. In terms of effect sizes, these are at best large enough to distinguish the patient group from the control group, but not large enough to classify an individual subject as being patient or control.”

“[T]he subtle cognitive decrements in speed of information processing and mental flexibility found in diabetic patients are not merely caused by acute metabolic derangements or psychological factors, but point to end-organ damage in the central nervous system. Although some uncertainty remains about the exact pathogenesis, several mechanisms through which diabetes may affect the brain have now been identified […] The issue whether or not repeated episodes of severe hypoglycaemia result in permanent mild cognitive impairment has been debated extensively in the literature. […] The meta-analysis on the effect of type 1 diabetes on cognition (1) does not support the idea that there are important negative effects from recurrent episodes of severe hypoglycaemia on cognitive functioning, and large prospective studies did not confirm the earlier observations […] there is no evidence for a linear relationship between recurrent episodes of hypoglycaemia and permanent brain dysfunction in adults. […] Cerebral microvascular pathology in diabetes may result in a decrease of regional cerebral blood flow and an alteration in cerebral metabolism, which could partly explain the occurrence of cognitive impairments. It could be hypothesised that vascular pathology disrupts white-matter integrity in a way that is akin to what one sees in peripheral neuropathy and as such could perhaps affect the integrity of neurotransmitter systems and as a consequence limits cognitive efficiency. These effects are likely to occur diffusely across the brain. Indeed, this is in line with MRI findings and other reports.”

“[An] important issue is the interaction between different disease variables. In particular, patients with diabetes onset before the age of 5 […] and patients with advanced microangiopathy might be more sensitive to the effects of hypoglycaemic episodes or elevated HbA1c levels. […] decrements in cognitive function have been observed as early as 2 years after the diagnosis (63). It is important to consider the possibility that the developing brain is more vulnerable to the effect of diabetes […] Diabetes has a marked effect on brain function and structure in children and adolescents. As a group, diabetic children are more likely to perform more poorly than their nondiabetic peers in the classroom and earn lower scores on measures of academic achievement and verbal intelligence. Specialized neuropsychological testing reveals evidence of dysfunction in a variety of cognitive domains, including sustained attention, visuoperceptual skills, and psychomotor speed. Children diagnosed early in life – before 7 years of age – appear to be most vulnerable, showing impairments on virtually all types of cognitive tests, with learning and memory skills being particularly affected. Results from neurophysiological, cerebrovascular, and neuroimaging studies also show evidence of CNS anomalies. Earlier research attributed diabetes-associated brain dysfunction to episodes of recurrent hypoglycemia, but more recent studies have generally failed to find strong support for that view.”

“[M]ethodological issues notwithstanding, extant research on diabetic children’s brain function has identified a number of themes […]. All other things being equal, children diagnosed with type 1 diabetes early in life – within the first 5–7 years of age – have the greatest risk of manifesting neurocognitive dysfunction, the magnitude of which is greater than that seen in children with a later onset of diabetes. The development of brain dysfunction seems to occur within a relatively brief period of time, often appearing within the first 2–3 years following diagnosis. It is not limited to performance on neuropsychological tests, but is manifested on a wide range of electrophysiological measures as marked neural slowing. Somewhat surprisingly, the magnitude of these effects does not seem to worsen appreciably with increasing duration of diabetes – at least through early adulthood. […] As a group, diabetic children earn somewhat lower grades in school as compared to their nondiabetic classmates, are more likely to fail or repeat a grade, perform more poorly on formal tests of academic achievement, and have lower IQ scores, particularly on tests of verbal intelligence.”

The most compelling evidence for a link between diabetes and poorer school outcomes has been provided by a Swedish population-based register study involving 5,159 children who developed diabetes between July 1997 and July 2000 and 1,330,968 nondiabetic children […] Those who developed diabetes very early in life (diagnosis before 2 years of age) had a significantly increased risk of not completing school as compared to either diabetic patients diagnosed after that age or to the reference population. Small, albeit statistically reliable between-group differences were noted in school marks, with diabetic children, regardless of age at diagnosis, consistently earning somewhat lower grades. Of note is their finding that the diabetic sample had a significantly lower likelihood of getting a high mark (passed with distinction or excellence) in two subjects and was less likely to take more advanced courses. The authors conclude that despite universal access to active diabetes care, diabetic children – particularly those with a very early disease onset – had a greatly increased risk of somewhat lower educational achievement […] Similar results have been reported by a number of smaller studies […] in the prospective Melbourne Royal Children’s Hospital (RCH) cohort study (22), […] only 68% of [the] diabetic sample completed 12 years of school, as compared to 85% of the nondiabetic comparison group […] Children with diabetes, especially those with an earlier onset, have also been found to require more remedial educational services and to be more likely to repeat a grade (25–28), to earn lower school grades over time (29), to experience somewhat greater school absenteeism (28, 30–32), to have a two to threefold increase in rates of depression (33– 35), and to manifest more externalizing behavior problems (25).”

“Children with diabetes have a greatly increased risk of manifesting mild neurocognitive dysfunction. This is an incontrovertible fact that has emerged from a large body of research conducted over the past 60 years […]. There is, however, less agreement about the details. […] On standardized tests of academic achievement, diabetic children generally perform somewhat worse than their healthy peers […] Performance on measures of verbal intelligence – particularly those that assess vocabulary knowledge and general information about the world – is frequently compromised in diabetic children (9, 14, 26, 40) and in adults (41) with a childhood onset of diabetes. The few studies that have followed subjects over time have noted that verbal IQ scores tend to decline as the duration of diabetes increases (13, 15, 29). These effects appear to be more pronounced in boys and in those children with an earlier onset of diabetes. Whether this phenomenon is a marker of cognitive decline or whether it reflects a delay in cognitive development cannot yet be determined […] it is possible, but remains unproven, that psychosocial processes (e.g., school absence, depression, distress, externalizing problems) (42), and/or multiple and prolonged periods of classroom inattention and reduced motivation secondary to acute and prolonged episodes of hypoglycemia (43–45) may be contributing to the poor academic outcomes characteristic of children with diabetes. Although it may seem more reasonable to attribute poorer school performance and lower IQ scores to diabetes-associated disruption of specific neurocognitive processes (e.g., attention, learning, memory) secondary to brain dysfunction, there is little compelling evidence to support that possibility at the present time.”

“Children and adults who develop diabetes within the first 5–7 years of life may show moderate cognitive dysfunction that can affect all cognitive domains, although the specific pattern varies, depending both on the cognitive domain assessed and on the child’s age at assessment. Data from a recent meta-analysis of 19 pediatric studies have indicated that effect sizes tend to range between ∼ 0.4 and 0.5 for measures of learning, memory, and attention, but are lower for other cognitive domains (47). For the younger child with an early onset of diabetes, decrements are particularly pronounced on visuospatial tasks that require copying complex designs, solving jigsaw puzzles, or using multi-colored blocks to reproduce designs, with girls more likely to earn lower scores than boys (8). By adolescence and early adulthood, gender differences are less apparent and deficits occur on measures of attention, mental efficiency, learning, memory, eye–hand coordination, and “executive functioning” (13, 26, 40, 48–50). Not only do children with an early onset of diabetes often – but not invariably – score lower than healthy comparison subjects, but a subset earn scores that fall into the “clinically impaired” range […]. According to one estimate, the prevalence of clinically significant impairment is approximately four times higher in those diagnosed within the first 6 years of life as compared to either those diagnosed after that age or to nondiabetic peers (25 vs. 6%) (49). Nevertheless, it is important to keep in mind that not all early onset diabetic children show cognitive dysfunction, and not all tests within a particular cognitive domain differentiate diabetic from nondiabetic subjects.”

“Slowed neural activity, measured at rest by electroencephalogram (EEG) and in response to sensory stimuli, is common in children with diabetes. On tests of auditory- or visual-evoked potentials (AEP; VEP), children and adolescents with more than a 2-year history of diabetes show significant slowing […] EEG recordings have also demonstrated abnormalities in diabetic adolescents in very good metabolic control. […] EEG abnormalities have also been associated with childhood diabetes. One large study noted that 26% of their diabetic subjects had abnormal EEG recordings, as compared to 7% of healthy controls […] diabetic children with EEG abnormalities recorded at diagnosis may be more likely to experience a seizure or coma (i.e., a severe hypoglycemic event) when blood glucose levels subsequently fall […] This intriguing possibility – that seizures occur in some diabetic children during hypoglycemia because of the presence of pre-existing brain dysfunction – requires further study.” 

“A very large body of research on adults with diabetes now demonstrates that the risk of developing a wide range of neurocognitive changes – poorer cognitive function, slower neural functioning, abnormalities in cerebral blood flow and brain metabolites, and reductions or alterations in gray and white-brain matter – is associated with chronically elevated blood glucose values […] Taken together, the limited animal research on this topic […] provides quite compelling support for the view that even relatively brief bouts of chronically elevated blood glucose values can induce structural and functional changes to the brain. […] [One pathophysiological model proposed is] the “diathesis” or vulnerability model […] According to this model, in the very young child diagnosed with diabetes, chronically elevated blood glucose levels interfere with normal brain maturation at a time when those neurodevelopmental processes are particularly labile, as they are during the first 5–7 years of life […]. The resulting alterations in brain organization that occur during this “sensitive period” will not only lead to delayed cognitive development and lasting cognitive dysfunction, but may also induce a predisposition or diathesis that increases the individual’s sensitivity to subsequent insults to the brain, as could be initiated by the prolonged neuroglycopenia that occurs during an episode of hypoglycemia. Data from most, but not all, research are consistent with that view. […] Research is only now beginning to focus on plausible pathophysiological mechanisms.”

After having read these chapters, I’m now sort-of-kind-of wondering to which extent my autism was/is also at least partly diabetes-mediated. There’s no evidence linking autism and diabetes presented in the chapters, but you do start to wonder even so – the central nervous system is complicated.. If diabetes did play a role there, that would probably be an argument for not considering potential diabetes-mediated brain changes in me as ‘minor’ despite my somewhat higher than average IQ (just to be clear, a high observed IQ in an individual does not preclude the possibility that diabetes had a negative IQ-effect – we don’t observe the counterfactual – but a high observed IQ does make a potential IQ-lowering effect less likely to have happened, all else equal).

December 21, 2016 Posted by | Books, Diabetes, Epidemiology, Medicine, Neurology, Personal | Leave a comment

Role of Biomarkers in Medicine

“The use of biomarkers in basic and clinical research has become routine in many areas of medicine. They are accepted as molecular signatures that have been well characterized and repeatedly shown to be capable of predicting relevant disease states or clinical outcomes. In Role of Biomarkers in Medicine, expert researchers in their individual field have reviewed many biomarkers or potential biomarkers in various types of diseases. The topics address numerous aspects of medicine, demonstrating the current conceptual status of biomarkers as clinical tools and as surrogate endpoints in clinical research.”

The above quote is from the preface of the book. Here’s my goodreads review. I have read about biomarkers before – for previous posts on this topic, see this link. I added the link in part because the coverage provided in this book is in my opinion generally of a somewhat lower quality than is the coverage that has been provided in some of the other books I’ve read on these topics. However the fact that the book is not amazing should probably not keep me from sharing some observations of interest from the book, which I have done in this post.

we suggest more precise studies to establish the exact role of this hormone […] additional studies are necessary […] there are conflicting results […] require further investigation […] more intervention studies with long-term follow-up are required. […] further studies need to be conducted […] further research is needed (There are a lot of comments like these in the book, I figured I should include a few in my coverage…)

“Cancer biomarkers (CB) are biomolecules produced either by the tumor cells or by other cells of the body in response to the tumor, and CB could be used as screening/early detection tool of cancer, diagnostic, prognostic, or predictor for the overall outcome of a patient. Moreover, cancer biomarkers may identify subpopulations of patients who are most likely to respond to a given therapy […] Unfortunately, […] only very few CB have been approved by the FDA as diagnostic or prognostic cancer markers […] 25 years ago, the clinical usefulness of CB was limited to be an effective tool for patient’s prognosis, surveillance, and therapy monitoring. […] CB have [since] been reported to be used also for screening of general population or risk groups, for differential diagnosis, and for clinical staging or stratification of cancer patients. Additionally, CB are used to estimate tumor burden and to substitute for a clinical endpoint and/or to measure clinical benefit, harm or lack of benefit, or harm [4, 18, 30]. Among commonly utilized biomarkers in clinical practice are PSA, AFP, CA125, and CEA.”

“Bladder cancer (BC) is the second most common malignancy in the urologic field. Preoperative predictive biomarkers of cancer progression and prognosis are imperative for optimizing […] treatment for patients with BC. […] Approximately 75–85% of BC cases are diagnosed as nonmuscle-invasive bladder cancer (NMIBC) […] NMIBC has a tendency to recur (50–70%) and may progress (10–20%) to a higher grade and/or muscle-invasive BC (MIBC) in time, which can lead to high cancer-specific mortality [2]. Histological tumor grade is one of the clinical factors associated with outcomes of patients with NMIBC. High-grade NMIBC generally exhibits more aggressive behavior than low-grade NMIBC, and it increases the risk of a poorer prognosis […] Cystoscopy and urine cytology are commonly used techniques for the diagnosis and surveillance of BC. Cystoscopy can identify […] most papillary and solid lesions, but this is highly invasive […] urine cytology is limited by examiner experience and low sensitivity. For these reasons, some tumor markers have been investigated […], but their sensitivity and specificity are limited [5] and they are unable to predict the clinical outcome of BC patients. […] Numerous efforts have been made to identify tumor markers. […] However, a serum marker that can serve as a reliable detection marker for BC has yet to be identified.”

“Endometrial cancer (EmCa) is the most common type of gynecological cancer. EmCa is the fourth most common cancer in the United States, which has been linked to increased incidence of obesity. […] there are no reliable biomarker tests for early detection of EmCa and treatment effectiveness. […] Approximately 75% of women with EmCa are postmenopausal; the most common symptom is postmenopausal bleeding […] Approximately 15% of women diagnosed with EmCa are younger than 50 years of age, while 5% are diagnosed before the age of 40 [29]. […] Roughly, half of the EmCa cases are linked to obesity. Obese women are four times more likely to develop EmCa when compared to normal weight women […] Obese individuals oftentimes exhibit resistance to leptin and show high levels of the adipokine in blood, which is known as leptin resistance […] prolonged exposure of leptin damages the hypothalamus causing it to become insensitive to the effects of leptin […] Evidence shows that leptin is an important pro-inflammatory, pro-angiogenic, and mitogenic factor for cancer. Leptin produced by cancer cells acts in an autocrine and paracrine manner to promote tumor cell proliferation, migration and invasion, pro-inflammation, and angiogenesis [58, 70]. High levels of leptin […] are associated with metastasis and decreased survival rates in breast cancer patients [58]. […] Metabolic syndrome including obesity, hypertension, insulin resistance, diabetes, and dyslipidemia increase the risk of developing multiple malignancies, particularly EmCa [30]. Younger women diagnosed with EmCa are usually obese, and their carcinomas show a well-differentiated histology [20].

“Normally, tumor suppressor genes act to inhibit or arrest cell proliferation and tumor development [37]. However; when mutated, tumor suppressors become inactive, thus permitting tumor growth. For example, mutations in p53 have been determined in various cancers such as breast, colon, lung, endometrium, leukemias, and carcinomas of many tissues. These p53 mutations are found in approximately 50% of all cancers [38]. Roughly 10–20% of endometrial carcinomas exhibit p53 mutations [37]. […] overexpression of mutated tumor suppressor p53 has been associated with Type II EmCa (poor histologic grade, non-endometrioid histology, advanced stage, and poor survival).”

“Increasing data indicate that oxidative stress is involved in the development of DR [diabetic retinopathy] [16–19]. The retina has a high content of polyunsaturated fatty acids and has the highest oxygen uptake and glucose oxidation relative to any other tissue. This phenomenon renders the retina more susceptible to oxidative stress [20]. […] Since long-term exposure to oxidative stress is strongly implicated in the pathogenesis of diabetic complications, polymorphic genes of detoxifying enzymes may be involved in the development of DR. […] A meta-analysis comprising 17 studies, including type 1 and type 2 diabetic patients from different ethnic origins, implied that the C (Ala) allele of the C47T polymorphism in the MnSOD gene had a significant protective effect against microvascular complications (DR and diabetic nephropathy) […] In the development of DR, superoxide levels are elevated in the retina, antioxidant defense system is compromised, MnSOD is inhibited, and mitochondria are swollen and dysfunctional [77,87–90]. Overexpression of MnSOD protects [against] diabetes-induced mitochondrial damage and the development of DR [19,91].”

Continuous high level of blood glucose in diabetes damages micro and macro blood vessels throughout the body by altering the endothelial cell lining of the blood vessels […] Diabetes threatens vision, and patients with diabetes develop cataracts at an earlier age and are nearly twice as likely to get glaucoma compared to non-diabetic[s] [3]. More than 75% of patients who have had diabetes mellitus for more than 20 years will develop diabetic retinopathy (DR) [4]. […] DR is a slow progressive retinal disease and occurs as a consequence of longstanding accumulated functional and structural impairment of the retina by diabetes. It is a multifactorial condition arising from the complex interplay between biochemical and metabolic abnormalities occurring in all cells of the retina. DR has been classically regarded as a microangiopathy of the retina, involving changes in the vascular wall leading to capillary occlusion and thereby retinal ischemia and leakage. And more recently, the neural defects in the retina are also being appreciated […]. Recently, various clinical investigators [have detected] neuronal dysfunction at very early stages of diabetes and numerous abnormalities in the retina can be identified even before the vascular pathology appears [76, 77], thus suggesting a direct effect of diabetes on the neural retina. […] An emerging issue in DR research is the focus on the mechanistic link between chronic low-grade inflammation and angiogenesis. Recent evidence has revealed that extracellular high-mobility group box-1 (HMGB1) protein acts as a potent proinflammatory cytokine that triggers inflammation and recruits leukocytes to the site of tissue damage, and exhibits angiogenic effects. The expression of HMGB1 is upregulated in epiretinal membranes and vitreous fluid from patients with proliferative DR and in the diabetic retina. […] HMGB1 may be a potential biomarker [for diabetic retinopathy] […] early blockade of HMGB1 may be an effective strategy to prevent the progression of DR.”

“High blood pressure is one of the leading risk factors for global mortality and is estimated to have caused 9.4 million deaths in 2010. A meta‐analysis which includes 1 million individuals has indicated that death from both CHD [coronary heart disease] and stroke increase progressively and linearly from BP levels as low as 115 mmHg systolic and 75 mmHg diastolic upwards [138]. The WHO [has] pointed out that a “reduction in systolic blood pressure of 10 mmHg is associated with a 22% reduction in coronary heart disease, 41% reduction in stroke in randomized trials, and a 41–46% reduction in cardiometabolic mortality in epidemiological studies” [139].”

Several reproducible studies have ascertained that individuals with autism demonstrate an abnormal brain 5-HT system […] peripheral alterations in the 5-HT system may be an important marker of central abnormalities in autism. […] In a recent study, Carminati et al. [129] tested the therapeutic efficacy of venlafaxine, an antidepressant drug that inhibits the reuptake of 5-HT, and [found] that venlafaxine at a low dose [resulted in] a substantial improvement in repetitive behaviors, restricted interests, social impairment, communication, and language. Venlafaxine probably acts via serotonergic mechanisms  […] OT [Oxytocin]-related studies in autism have repeatedly reported lower blood OT level in autistic patients compared to age- and gender-matched control subjects […] autistic patients demonstrate an altered neuroinflammatory response throughout their lives; they also show increased astrocyte and microglia inflammatory response in the cortex and the cerebellum  [47, 48].”

November 3, 2016 Posted by | autism, Books, Cancer/oncology, Cardiology, Diabetes, Epidemiology, Genetics, Immunology, Medicine, Neurology, Pharmacology | Leave a comment

A couple of lectures and a little bit of random stuff

i. Two lectures from the Institute for Advanced Studies:

The IAS has recently uploaded a large number of lectures on youtube, and the ones I blog here are a few of those where you can actually tell from the title what the lecture is about; I find it outright weird that these people don’t include the topic covered in the lecture in their lecture titles.

As for the video above, as usual for the IAS videos it’s annoying that you can’t hear the questions asked by the audience, but the sound quality of this video is at least quite a bit better than the sound quality of the video below (which has a couple of really annoying sequences, in particular around the 15-16 minutes mark (it gets better), where the image is also causing problems, and in the last couple of minutes of the Q&A things are also not exactly optimal as the lecturer leaves the area covered by the camera in order to write something on the blackboard – but you don’t know what he’s writing and you can’t see the lecturer, because the camera isn’t following him). I found most of the above lecture easier to follow than I did the lecture posted below, though in either case you’ll probably not understand all of it unless you’re an astrophysicist – you definitely won’t in case of the latter lecture. I found it helpful to look up a few topics along the way, e.g. the wiki articles about the virial theorem (/also dealing with virial mass/radius), active galactic nucleus (this is the ‘AGN’ she refers to repeatedly), and the Tully–Fisher relation.

Given how many questions are asked along the way it’s really annoying that you in most cases can’t hear what people are asking about – this is definitely an area where there’s room for improvement in the context of the IAS videos. The lecture was not easy to follow but I figured along the way that I understood enough of it to make it worth watching the lecture to the end (though I’d say you’ll not miss much if you stop after the lecture – around the 1.05 hours mark – and skip the subsequent Q&A). I’ve relatively recently read about related topics, e.g. pulsar formation and wave- and fluid dynamics, and if I had not I probably would not have watched this lecture to the end.

ii. A vocabulary.com update. I’m slowly working my way up to the ‘Running Dictionary’ rank (I’m only a walking dictionary at this point); here’s some stuff from my progress page:

Vocab
I recently learned from a note added to a list that I’ve actually learned a very large proportion of all words available on vocabulary.com, which probably also means that I may have been too harsh on the word selection algorithm in past posts here on the blog; if there aren’t (/m)any new words left to learn it should not be surprising that the algorithm presents me with words I’ve already mastered, and it’s not the algorithm’s fault that there aren’t more words available for me to learn (well, it is to the extent that you’re of the opinion that questions should be automatically created by the algorithm as well, but I don’t think we’re quite there yet at this point). The aforementioned note was added in June, and here’s the important part: “there are words on your list that Vocabulary.com can’t teach yet. Vocabulary.com can teach over 12,000 words, but sadly, these aren’t among them”. ‘Over 12.000’ – and I’ve mastered 11.300. When the proportion of mastered words is this high, not only will the default random word algorithm mostly present you with questions related to words you’ve already mastered; but it actually also starts to get hard to find lists with many words you’ve not already mastered – I’ll often load lists with one hundred words and then realize that I’ve mastered every word on the list. This is annoying if you have a desire to continually be presented with both new words as well as old ones. Unless vocabulary.com increases the rate with which they add new words I’ll run out of new words to learn, and if that happens I’m sure it’ll be much more difficult for me to find motivation to use the site.

With all that stuff out of the way, if you’re not a regular user of the site I should note – again – that it’s an excellent resource if you desire to increase your vocabulary. Below is a list of words I’ve encountered on the site in recent weeks(/months?):

Copaceticfrumpyelisiontermagantharridanquondam, funambulist, phantasmagoriaeyelet, cachinnate, wilt, quidnunc, flocculent, galoot, frangible, prevaricate, clarion, trivet, noisome, revenant, myrmidon (I have included this word once before in a post of this type, but it is in my opinion a very nice word with which more people should be familiar…), debenture, teeter, tart, satiny, romp, auricular, terpsichorean, poultice, ululation, fusty, tangy, honorarium, eyas, bumptious, muckraker, bayou, hobble, omphaloskepsis, extemporize, virago, rarefaction, flibbertigibbet, finagle, emollient.

iii. I don’t think I’d do things exactly the way she’s suggesting here, but the general idea/approach seems to me appealing enough for it to be worth at least keeping in mind if I ever decide to start dating/looking for a partner.

iv. Some wikipedia links:

Tarrare (featured). A man with odd eating habits and an interesting employment history (“Dr. Courville was keen to continue his investigations into Tarrare’s eating habits and digestive system, and approached General Alexandre de Beauharnais with a suggestion that Tarrare’s unusual abilities and behaviour could be put to military use.[9] A document was placed inside a wooden box which was in turn fed to Tarrare. Two days later, the box was retrieved from his excrement, with the document still in legible condition.[9][17] Courville proposed to de Beauharnais that Tarrare could thus serve as a military courier, carrying documents securely through enemy territory with no risk of their being found if he were searched.” Yeah…).

Cauda equina syndromeCastleman’s disease, Astereognosis, Familial dysautonomia, Homonymous hemianopsia, Amaurosis fugax. All of these are of course related to content covered in the Handbook.

1740 Batavia massacre (featured).

v. I am also fun.

October 30, 2015 Posted by | Astronomy, History, Immunology, language, Lectures, Medicine, Neurology, Personal, Physics, Random stuff, Wikipedia | Leave a comment

Peripheral Neuropathy & Neuropathic Pain: Into the light (II)

Here’s my first post about the book. As I mentioned in that post, I figured I should limit detailed coverage to the parts of the book dealing with stuff related to diabetic/metabolic neuropathies. There’s a chapter specifically about ‘diabetic and uraemic neuropathies’ in the book and most of the coverage below relates to content covered in that chapter, but I have also included some related observations from other parts of the book as they seemed relevant.

It is noted in the book’s coverage that diabetes is the commonest cause of neuropathy in industrialized countries. There are many ways in which diabetes can affect the nervous system, and not all diabetes-related neuropathies affect peripheral nerves. Apart from distal symmetric polyneuropathy, which can probably in this context be thought of as ‘classic diabetic neuropathy’, focal or multifocal involvement of the peripheral nervous system is also common, and so is autonomic neuropathy. Diabetics are also at increased risk of inflammatory neuropathies such as CIDP – chronic inflammatory demyelinating polyneuropathy (about which the book also has a chapter). Late stage complications of diabetes usually relate to some extent to vessel wall abnormalities and their effects, and the blood vessels supplying the peripheral nerves can be affected just like all other blood vessels; in that context it is of interest to note that the author mentions elsewhere in the book that “tissue ischaemia is more likely to be symptomatic in nerves than in most other organs”. According to the author there isn’t really a great way to classify all the various manifestations of diabetic neuropathy, but most of them fall into one of three groups – distal symmetrical sensorimotor (length-dependent) polyneuropathy (DSSP); autonomic neuropathy; and focal- and multifocal neuropathy. The first one of these is by far the most common, and it is predominantly a sensory neuropathy (‘can you feel this?’ ‘does this hurt?’ ‘Is this water hot or cold?’ – as opposed to motor neuropathy: ‘can you move your arm?’) with no motor deficit.

Neuropathies in diabetics are common – how common? The author notes that the prevalence in several population-based surveys has been found to be around 30% “in studies using restrictive definitions”. The author does not mention this, but given that diabetic neuropathy usually has an insidious onset and given that diabetes-related sensory neuropathy “can be totally asymptomatic”, survey-based measures are if anything likely to underestimate prevalence. Risk increases with age and duration of diabetes; the prevalence of diabetic peripheral neuropathy is more than 50% in type 1 diabetics above the age of 60.

DSSP may lead to numbness, burning feet, a pins and needles sensation and piercing/stabbing pain in affected limbs. The ‘symmetric’ part of the abbreviation means that it usually affects both sides of the body, instead of e.g. just one foot or hand. The length-dependence mentioned in the parenthesis earlier relates in a way to the pathophysiological process. The axons of the peripheral nervous system lack ribosomes, and this means that essential proteins and enzymes needed in distal regions of the nervous system need to be transported great distances through the axons – which again means that neurons with long axons are particularly vulnerable to toxic or metabolic disturbances (introducing a length-dependence aspect in terms of which nerves are affected) which may lead to so-called dying-back axonal degeneration. The sensory loss can be restricted to the toes, extend over the feet, or it can migrate even further up the limbs – when sensory loss extends above the knee, signs and symptoms of nerve damage will usually also be observed in the fingers/hands/forearms. In generalized neuropathies a distinction can be made in terms of which type of nerve fibres are predominantly involved. When small fibres are most affected, sensory effects relating to pain- and temperature perception predominate, whereas light touch, position and vibratory senses are relatively preserved; on the other hand abnormalities of proprioception and sensitivity to light touch, often accompanied by motor deficits, will predominate if larger myelinated fibres are involved. DSSP is a small fibre neuropathy.

One of the ‘problems’ in diabetic neuropathy is actually that whereas sensation is affected, motor function often is not. This might be considered much better than the alternative, but unimpaired motor function actually relates closely to how damage often occurs. Wounds/ulcers developing on the soles of the feet (plantar ulcers) are very common in conditions in which there is sensation loss but no motor involvement/loss of strength; people with absent pain sensation will not know when their feet get hurt, e.g. because of a stone in the shoe or other forms of micro-trauma, but they’re still able to walk around relatively unimpaired and the absence of protective sensation in the limbs can thus lead to overuse of joints and accidental self-injury. A substantial proportion of diabetics with peripheral neuropathy also have lower limb ischaemia from peripheral artery disease, which further increases risk, but even in the absence of ischaemia things can go very wrong (for more details, see Edmonds, Foster, and Sanders – I should perhaps warn that the picture in that link is not a great appetite-stimulant). Of course one related problem here is that you can’t just stop moving around in order to avoid these problems once you’re aware that you have peripheral sensory neuropathy; inactivity will lead to muscle atrophy and ischaemia, and that’s not good for your feet either. The neuropathy may not ‘just’ lead to ulcers, but may also lead to the foot becoming deformed – the incidence of neuroarthropathy is approximately 2%/year in diabetics with peripheral neuropathy. Foot deformity is sometimes of acute onset and may be completely painless, despite leading to (painless) fractures and disorganization of joints. In the context of ulcers it is important that foot ulcers often take a *very* long time to heal, and so they provide excellent entry points for bacteria which among other things can cause chronic osteomyelitis (infection and inflammation of the bone and bone marrow). Pronounced motor involvement is as mentioned often absent in DSSP, but it does sometimes occur, usually at a late stage.

The author notes repeatedly in the text that peripheral neuropathy is sometimes the presenting symptom in type 2 diabetes, and I thought I should include that observation here as well. The high blood glucose may not be what leads the patient to see a doctor – sometimes the fact that he can no longer feel his toes is. At that point the nerve damage which has already occurred will of course usually be irreversible.

When the autonomic nervous system is affected (this is called Diabetic Autonomic Neuropathy, -DAN), this can lead to a variety of different symptoms. Effects of orthostatic hypotension (-OH) are frequent complaints; blackouts, faintness and dizziness or visual obscuration on standing are not always due to side effects of blood pressure medications. The author notes that OH can be aggravated by tricyclic antidepressants which are often used for treating chronic neuropathic pain (diabetics with autonomous nervous system disorder will often have, sometimes painful, peripheral neuropathy as well). Neurogenic male impotence seems to be “extremely common”; this leads to the absence of an erection at any time under any circumstances. The bladder may also be involved, which can lead to increased intervals between voiding and residual urine in the bladder after voiding, which can lead to UTIs. It is noted that retrograde ejaculation is frequent in people with bladder atony. The gastrointestinal system can be affected; this is often asymptomatic, but may lead to diarrhea and constipation causing weight loss and malnutrition. Associated diarrhea may be accompanied by fecal incontinence. DAN can lead to hypoglycemia unawareness, making glycemic control more difficult to accomplish. Sweating disorders are common in the feet. When a limb is affected by neuropathy the limb may lose its ability to sweat, and this may lead to other parts of the body (e.g. the head or upper trunk) engaging in ‘compensatory sweating’ to maintain temperature control. Abnormal pupil responses, e.g. in the form of reduced light reflexes and constricted pupils (miosis), are common in diabetics.

Focal (one nerve) and occasionally also multi-focal (more than one nerve) neuropathic syndromes also occur in the diabetic setting. The book spends quite a bit of time talking about what different nerves do and what happens when they stop working, so it’s hard to paint a broad picture of how these types of problems may present – it all depends on which nerve(s) is (are) affected. Usually in the setting of these disorders the long-term prognosis is good, or at least better than in the setting of DSSP; nerve damage is often not permanent. It seems that in terms of cranial nerve involvement, oculomotor nerve palsies are the most common, but still quite rare, affecting 1-2% of diabetics. Symptoms are rapid onset pain followed by double vision, and “spontaneous and complete recovery invariably occurs within 2-3 months” – I would like to note that as far as diabetes complications go, this is probably about as good as it gets… In so-called proximal diabetic neuropathy (-PDN), another type of mononeuropathy/focal neuropathy, the thighs are involved, with numbness or pain, often of a burning character which is worse at night, as well as muscle wasting. That syndrome progresses over weeks or months, after which the condition usually stabilizes and the pain improves, though residual muscle weakness seems to be common. Unlike in the case of DSSP, deficits in PDN are usually asymmetric, and both motor involvement and gradual recovery is common – it’s important to note in this context that DSSP virtually never improves spontaneously and often has a progressive course. Multi-focal neuropathies affect only a small proportion of diabetics, and in terms of outcome patterns they might be said to lie somewhere in between mononeuropathies and DSSP; outcomes are better than in the case of DSSP, but long-term sequelae are common.

Diabetics are at increased risk of developing pressure palsies in general. According to the author carpal tunnel syndrome occurs in 12% of diabetic patients, and “the incidence of ulnar neuropathy due to microlesions at the elbow level is high”.

In diabetics with renal failure caused by diabetic nephropathy (or presumably for that matter renal failure caused by other things as well, but most diabetics with kidney failure will have diabetic nephropathy) neuropathy is common and often severe. Renal failure impairs nerve function and is responsible for sometimes severe motor deficits in these patients. “Recovery from motor deficits is usually good after kidney transplant”. Carpal tunnel syndrome is very common in patients on long-term dialysis; 20 to 50 % of patients dialysed for 10 years or more are reported to have carpal tunnel syndrome. The presence of neuropathy in renal patients is closely related to renal function; the lower renal function, the more likely neurological symptoms become.

As you’ll learn from this book, a lot of things can cause peripheral neuropathies – and so the author notes that “In focal neuropathy occurring in diabetic patients, a neuropathy of another origin must always be excluded.” It’s not always diabetes, and sometimes missing the true cause can be a really bad thing; for example cancer-associated paraneoplastic syndromes are often associated with neuropathy (“paraneoplastic syndromes affect the PNS [Peripheral Nervous System] in up to one third of patients with solid tumors”), and so missing ‘the true cause’ in the case of a focal neuropathy may mean missing a growing tumour.

In terms of treatment options, “There is no specific treatment for distal symmetric polyneuropathy.” Complications can be treated/ideally prevented, but we have no drugs the primary effects of which are to specifically stop the nerves from dying. Treatment of autonomic neuropathy mostly relates to treating symptoms, in particular symptomatic OH. Treatment of proximal diabetic neuropathy, which is often very painful, relates only to pain management. Multifocal diabetic neuropathy can be treated with corticosteroids, minimizing inflammation.

Due to how common diabetic neuropathy is, most controlled studies on treatment options for neuropathic pain have involved patients with distal diabetic polyneuropathy. Various treatment options exist in the context of peripheral neuropathies, including antidepressants, antiepileptic drugs and opioids, as well as topical patches. In general pharmacological treatments will not cause anywhere near complete pain relief: “For patients receiving pharmacological treatment, the average pain reduction is about 20-30%, and only 20-35% of patients will achieve at least a 50% pain reduction with available drugs. […] often only partial pain relief from neuropathic pain can be expected, and […] sensory deficits are unlikely to respond to treatment.” Treatment of neuropathic pain is often a trial-and-error process.

October 17, 2015 Posted by | Books, Cancer/oncology, Diabetes, Epidemiology, Medicine, Neurology, Pharmacology | Leave a comment

Peripheral Neuropathy & Neuropathic Pain: Into the light (I)

“Peripheral neuropathy is a common medical condition, the diagnosis of which is often protracted or delayed. It is not always easy to relate a neuropathy to a specific cause. Many people do not receive a full diagnosis, their neuropathy often being described as ‘idiopathic’ or ‘cryptogenic’. It is said that in Europe, one of the most common causes is diabetes mellitus but there are also many other known potential causes. The difficulty of diagnosis, the limited number of treatment options, a perceived lack of knowledge of the subject — except in specialised clinics, the number of which are limited — all add to the difficulties which many neuropathy patients have to face. Another additional problem for many patients is that once having received a full, or even a partial diagnosis, they are then often discharged back to their primary healthcare team who, in many instances, know little about this condition and how it may impact upon their patients’ lives. In order to help bridge this gap in medical knowledge and to give healthcare providers a better understanding of this often distressing condition, The Neuropathy Trust has commissioned a new book on this complex topic.

As well as covering the anatomy of the nervous system and the basic pathological processes that may affect the peripheral nerves, the book covers a whole range of neuropathic conditions. These include, for example, Guillain Barre syndrome, chronic inflammatory demyelinating polyneuropathy, vasculitic neuropathies, infectious neuropathies, diabetic and other metabolic neuropathies, hereditary neuropathies and neuropathies in patients with cancer.”

The stuff above is the part of the amazon book description I decided to include when I added the book to goodreads.

The book is dense. There are a lot of terms defined in the book and a lot of topics covered. Despite being a quite shortish book only a couple hundred pages long (compare for example with related books like this one), it’s still the sort of book which many people might consider using as a reference work (I certainly consider doing that). The author really knows his stuff. According to the website of the European Neurological Society, “The ENS has now become the most prominent society of neurologists on the European Continent with a total of 2300 (including all categories) members from 60 countires [sic] worldwide.” I mention this because five years ago Gérard Said, the author, became the President of the ENS. He’s done/accomplished a lot of stuff besides that, the link has more details about him and what’s he’s done but what it boils down to is that this guy as already mentioned really knows his stuff. I disliked the comment on the front cover of the book that it was Written by one of the world’s leading experts and I at first considered it a decent argument against reading the book, but actually it’s probably both a fair and accurate statement; it seems like this guy really is one of the top guys in his field (I have no clue why someone like this does not have a wikipedia page whereas [random celebrity whose name I don’t know] does – well, I do have a clue, but…).

I don’t find the book particularly hard to read, but I’m frequently looking stuff up and I’ve read textbooks dealing with similar topics before (see e.g. here and here) – maybe I’m underestimating how difficult the book might be to read and understand for someone without much medical knowledge, but I think you should be perfectly able to get through the book without already having a detailed understanding of the neurological system; in my opinion the book is potentially useful for patients as well as medical practitioners, at least if the patient is willing to put in some work. An extensive glossary is included at the beginning of the book, defining most of the terms with which people might be unfamiliar. If you were wondering why I looked up so many words and concepts on wikipedia and other online sources (see below) in spite of the glossary, I should note that this is how I generally read books like this one; wiki or google will often provide additional details compared to the information included in standard glossaries, and often it’s even faster to look up such stuff online than it might be to locate the definition in the book. Another big reason for looking up key terms online was that I decided early on that a link collection like the one included below might be the best way to illustrate here on the blog which kind of content is covered in the book. Regardless of how you decide to look up stuff along the way, you should definitely not skip the definitions included in the glossary before reading the book proper – many of the terms you won’t be able to remember just on account of having read the words and definitions once or twice, but it’s definitely a good idea to have a look even so before moving on; this is probably the first book I’ve read in which the glossary was located at the front of the book instead of somewhere in the back, and it’s not a coincidence that the author decided to organize the book this way.

As a small aside, I thought this might be a reasonable place to add a ‘meta’ comment related to my book posts more generally. I’ve been considering writing slightly shorter posts about the non-fiction books I’m reading/have read; ‘classical posts’ of the kind I’ve written a lot of in the past can easily end up taking four-five hours for me to write and edit, and this means that if I don’t write short posts about the books I may easily end up not blogging them at all. This is an undesirable outcome for me. What I’ve been doing instead lately is to review more books on goodreads than I used to do; the idea being that if I end up not blogging the book, I’ll at least have reviewed it on goodreads. This incidentally means that if you want to keep track of my reading these days and would like to know what I think about the books I’m reading, the front page of this blog is no longer enough; you may need to also pay attention to my activities on goodreads or keep track of my reading via this link (I update that book list very often, usually every time I’ve finished a book). I don’t like to ‘branch out’ like that, but I also don’t like the idea of cross-posting goodreads reviews on the blog, and recently I’ve found it hard to know how to do these things optimally – this is where I’ve ended up. These days I’ll usually add a goodreads review of a non-fiction book quite shortly after I’ve finished the book, especially if I’m not sure if I’ll blog the book later.

Okay, back to the book: I think I’ll limit semi-detailed discussion of the book’s contents to the stuff included about diabetic/metabolic neuropathies, and although I’ve already encountered some relevant content and useful observations on that topic at this point, I have not yet read the chapter devoted to this topic. So you should expect me to post another post about this book some time in the future. I’ve read roughly half the book at this point and as mentioned in an earlier update on goodreads I’m seriously considering giving this book a five star rating. The book has way too much stuff to talk about all of it in detail, so what I’ll do below is to add some links to topics/terms/etc. discussed in the coverage so far which I looked up along the way, to give you a few more details than did the quote at the beginning:

Peripheral neuropathy.
Spinal nerves.
Anterior grey column.
Motor neuron.
Afferent nerve fiber.
Interneuron.
Polyneuropathy.
Nodes of Ranvier.
Myokymia.
Fasciculation.
Neuromyotonia.
Syringomyelia.
Charcot–Marie–Tooth neuropathy.
Guillain–Barré syndrome.
Acute motor axonal neuropathy.
Dysautonomia.
POEMS syndrome.
Monoclonal gammopathy of undetermined significance.
Plasmacytoma.
Vasa nervorum.
Vasculitic neuropathy.
Granulomatosis with polyangiitis.
Churg-Strauss syndrome.
Mononeuritis Multiplex.

October 12, 2015 Posted by | Books, Diabetes, Medicine, meta, Neurology | Leave a comment

Cognitive Psychology (I)

I could theoretically write a lot of posts about this handbook, but I’m probably not going to do that. As I’ve mentioned before I own a physical copy of this book, and blogging physical books is a pain in the neck compared to blogging e-books – this is one of the main reasons why I’m only now starting to blog the book, despite having finished it some time ago.

The book is a 600+ pages long handbook (752 pages if you include glossary, index etc.), and it has 16 chapters on various topics. Though I’m far from sure, I’d estimate that I spent something like 50 hours on the book altogether so far – 3 hours per chapter on average – and that’s just for ‘reading the pages’, so to speak; if I do decide to blog this book in any amount of detail, the amount of time spent on the material in there will go up quite a bit.

So what’s the book about – what is ‘cognitive psychology’? Here are a few remarks on these topics from the preface and the first chapter:

“the leading contemporary approach to human cognition involves studying the brain as well as behaviour. We have used the term “cognitive psychology” in the title of this book to refer to this approach, which forms the basis for our coverage of human cognition. Note, however, that the term “cognitive neuroscience” is often used to describe this approach. […] Note that the distinction between cognitive psychology and cognitive neuroscience is often blurred – the term ‘cognitive psychology” can be used in a broader sense to include cognitive neuroscience. Indeed, it is in that broader sense that it is used in the title of this book.”

The first chapter – about ‘approaches to human cognition’ – is a bit dense, but I decided to talk a little about it anyway because it seemed like a good way to give you some idea about what the book is about and which sort of content you’ll encounter in it. In the chapter the authors outline four different approaches to human cognition and talk about each of these in a bit of detail. Experimental cognitive psychology is an approach which basically limits itself to behavioural evidence. What they term cognitive neuroscience is an approach using evidence from both behaviour and the brain (that can be accomplished by having people do stuff while their brain activity is being monitored). Cognitive neuropsychology is an approach where you try to use data from brain-damaged individuals to help understand how normal cognition works. The last approach, computational cognitive science, I recently dealt with in the Science of Reading handbook – this approach involves constructing computational models to understand/simulate specific aspects of human cognition. All four approaches are used throughout the book to obtain a greater understanding of the topics covered.

The introductory chapter also gives the reader some information about what the brain looks like and how it’s structured, adds some comments about distinctions between various forms of processing, such as bottom-up processing and top-down processing and serial processing and parallel processing, and adds information about common techniques used to study brain activity in neuroscience (single-unit recording, event-related potentials, positron emission tomography, fMRI, efMRI, magnetoencephalography, and transcranial magnetic stimulation). I don’t want to go too much into the specifics of all those topics here, but I should note that I was unaware of the existence of TMS (transcranial magnetic stimulation) research methodologies and that it sounds like an interesting approach; basically what people do when they use this approach is to use magnetic pulses to try to (briefly, for a short amount of time) disrupt the functioning of some area of the brain and then evaluate performance on cognitive tasks performed while the brain area in question is disrupted – if people perform more poorly on a given task when the brain area in question is disrupted by the magnetic field, it might indicate that the brain area is involved in that task. For various reasons it’s not unproblematic to interpret the results of TMS research and there are various limitations to the application of this method, but this is experimental manipulation of a kind I’d basically assumed did not exist in this field before I started out reading the book.

It’s noted in the first chapter that: “much research in cognitive psychology suffers from a relative lack of ecological validity […] and paradigm specificity (findings do not generalise from one paradigm to others). The same limitations apply to cognitive neuroscience since cognitive neuroscientists generally use tasks previously developed by cognitive psychologists. Indeed, the problem of ecological validity may be greater in cognitive neuroscience.” In the context of cognitive neuropsychology, there are also various problems which I’m reasonably sure I’ve talked about here before – for example brain damage is rarely conveniently localized to just one brain area the researcher happens to be interested in, and the use of compensatory strategies by individuals with brain damage may cause problems with interpretation. Small sample sizes and large patient heterogeneities within these samples also do not help. As for the last approach, computational cognitive science, the problems mentioned are probably mostly the ones you’d expect; the models developed are rarely used to make new predictions because they’re often too general to really make them at all easy to evaluate one way or the other (lots of free parameters you can fit however you like), and despite their complexity they tend to ignore a lot of presumably highly relevant details.

The above was an outline of some stuff covered in the first chapter. The book as mentioned has 16 chapters. ‘Part 1’ deals with visual perception and attention – there’s a lot of stuff about that kind of thing in the book, almost 200 pages – and includes chapters about ‘basic processes in visual perception’, ‘object and face recognition’, ‘perception, motion, and action’, and ‘attention and performance’. Part 2 deals with memory, including chapters about ‘learning, memory, and forgetting’, ‘long-term memory systems’ and ‘everyday memory’. That part I found interesting and I hope I’ll manage to find the time to cover some of that stuff here later on. Part 3 deals with language and includes chapters about ‘reading and speech perception’, ‘language comprehension’, and ‘language production’. I recall wondering a long time ago on this blog if people doing research on those kinds of topics distinguished between language production and language comprehension; it’s pretty obvious that they do.. Part 5 deals with ‘thinking and reasoning’ and includes chapters about ‘problem solving and expertise’, ‘judgment and decision making’, and ‘inductive and deductive reasoning’. Interestingly the first of these chapters talks quite a bit about chess, because chess expertise is one of the research areas people have looked at when looking at the topic of expertise. I may decide to talk about these things later on, but I’m not sure I’ll cover the stuff in part 5 in much detail because Gigerenzer (whose research the authors discuss in chapter 13) covers some related topics in his book Simply Rational, which I’m currently reading, and I frankly like his coverage better (I should perhaps clarify in light of the previous remarks that Gigerenzer does not cover chess, but rather talks about other topics also covered in that section – the coverage overlap relates to Gigerenzer’s work on heuristics). The last part of the book has a chapter on cognition and emotion and a chapter about consciousness.

As you read the chapters, the authors start out by outlining some key features/distinctions of interest. They talk about what the specific theory/hypothesis/etc. is about, then they talk about the research results, and then they give their own evaluation of the research and conclude the coverage with outlining some limitations of the available research. Multiple topics are covered this way – presentation, research, evaluation, limitations – in each chapter, and when multiple competing hypotheses/approaches have been presented the evaluations will highlight strengths and weaknesses of each approach. Along the way you’ll encounter boxes at the bottom of the pages with bolded ‘key terms’ and definitions of those terms, as well as figures and tables with research results and illustrations of brain areas involved; key terms are also bolded in the text, so even if you don’t completely destroy the book by painting all over the pages with highlighters of different colours the way I do, it should be reasonably easy to navigate the content on a second reading. Usually the research on a given topic will be divided into sections if multiple approaches have been used to elucidate problems of interest; so there’ll be one section dealing with cognitive neuropsychology research, and another section about the cognitive neuroscience results. All chapters end with a brief outline of key terms/models/approaches encountered in the chapter and some of the main results discussed. The book is well structured. Coverage is in my opinion a bit superficial, which is one of the main reasons why I only gave the book three stars, and the authors are not always as skeptical as I’d have liked them to be – I did not always agree with the conclusions they drew from the research they discussed in the chapters, and occasionally I think they miss alternative explanations or misinterpret what the data is telling us. Some of the theoretical approaches they discuss in the text I frankly considered (/next to) worthless and a waste of time. It’s been a while since I finished the book and of course I don’t recall details as well as I’d like, but from what I remember and what I’ve gathered from a brief skim again while writing the post it’s far from a terrible book and on a general note it covers some interesting stuff – we’ll see how much of it I’ll manage to talk about here on the blog in the time to come. Regardless of how much more time I’ll be able to devote to the book here on the blog, this post should at least have given you some idea about which topics are covered in the book and how they’re covered.

September 24, 2015 Posted by | Books, Neurology, Psychology | Leave a comment

Stuff

Sorry for the infrequent updates. I realized blogging Wodehouse books takes more time than I’d imagined, so posting this sort of stuff is probably a better idea.

i. Dunkirk evacuation (wikipedia ‘good article’). Fascinating article, as are a few of the related ones which I’ve also been reading (e.g. Operation Ariel).

“On the first day of the evacuation, only 7,669 men were evacuated, but by the end of the eighth day, a total of 338,226 soldiers had been rescued by a hastily assembled fleet of over 800 boats. Many of the troops were able to embark from the harbour’s protective mole onto 39 British destroyers and other large ships, while others had to wade out from the beaches, waiting for hours in the shoulder-deep water. Some were ferried from the beaches to the larger ships by the famous little ships of Dunkirk, a flotilla of hundreds of merchant marine boats, fishing boats, pleasure craft, and lifeboats called into service for the emergency. The BEF lost 68,000 soldiers during the French campaign and had to abandon nearly all of their tanks, vehicles, and other equipment.”

One way to make sense of the scale of the operations here is to compare them with the naval activities on D-day four years later. The British evacuated more people from France during three consecutive days in 1940 (30th and 31st of May, and 1st of June) than the Allies (Americans and British combined) landed on D-day four years later, and the British evacuated roughly as many people on the 31st of May (68,014) as they landed by sea on D-day (75,215). Here’s a part of the story I did not know:

“Three British divisions and a host of logistic and labour troops were cut off to the south of the Somme by the German “race to the sea”. At the end of May, a further two divisions began moving to France with the hope of establishing a Second BEF. The majority of the 51st (Highland) Division was forced to surrender on 12 June, but almost 192,000 Allied personnel, 144,000 of them British, were evacuated through various French ports from 15–25 June under the codename Operation Ariel.[104] […] More than 100,000 evacuated French troops were quickly and efficiently shuttled to camps in various parts of southwestern England, where they were temporarily lodged before being repatriated.[106] British ships ferried French troops to Brest, Cherbourg, and other ports in Normandy and Brittany, although only about half of the repatriated troops were deployed against the Germans before the surrender of France. For many French soldiers, the Dunkirk evacuation represented only a few weeks’ delay before being killed or captured by the German army after their return to France.[107]

ii. A pretty awesome display by the current world chess champion:

If you feel the same way I do about Maurice Ashley, you’ll probably want to skip the first few minutes of this video. Don’t miss the games, though – this is great stuff. Do keep in mind when watching this video that the clock is a really important part of this event; other players in the past have played a lot more people at the same time while blindfolded than Carlsen does here – “Although not a full-time chess professional [Najdorf] was one of the world’s leading chess players in the 1950s and 1960s and he excelled in playing blindfold chess: he broke the world record twice, by playing blindfold 40 games in Rosario, 1943,[8] and 45 in São Paulo, 1947, becoming the world blindfold chess champion” (link) – but a game clock changes things a lot. A few comments and discussion here.
In very slightly related news, I recently got in my first win against a grandmaster in a bullet game on the ICC.

iii. Gastric-brooding frog.

Rheobatrachus_silus

“The genus was unique because it contained the only two known frog species that incubated the prejuvenile stages of their offspring in the stomach of the mother.[3] […] What makes these frogs unique among all frog species is their form of parental care. Following external fertilization by the male, the female would take the eggs or embryos into her mouth and swallow them.[19] […] Eggs found in females measured up to 5.1 mm in diameter and had large yolk supplies. These large supplies are common among species that live entirely off yolk during their development. Most female frogs had around 40 ripe eggs, almost double that of the number of juveniles ever found in the stomach (21–26). This means one of two things, that the female fails to swallow all the eggs or the first few eggs to be swallowed are digested. […] During the period that the offspring were present in the stomach the frog would not eat. […] The birth process was widely spaced and may have occurred over a period of as long as a week. However, if disturbed the female may regurgitate all the young frogs in a single act of propulsive vomiting.”

Fascinating creatures.. Unfortunately they’re no longer around (they’re classified as extinct).

iv. I’m sort of conflicted about what to think about this:

“Epidemiological studies show that patients with type-2-diabetes (T2DM) and individuals with a diabetes-independent elevation in blood glucose have an increased risk for developing dementia, specifically dementia due to Alzheimer’s disease (AD). These observations suggest that abnormal glucose metabolism likely plays a role in some aspects of AD pathogenesis, leading us to investigate the link between aberrant glucose metabolism, T2DM, and AD in murine models. […] Recent epidemiological studies demonstrate that individuals with type-2 diabetes (T2DM) are 2–4 times more likely to develop AD (35), individuals with elevated blood glucose levels are at an increased risk to develop dementia (5), and those with elevated blood glucose levels have a more rapid conversion from mild cognitive impairment (MCI) to AD (6), suggesting that disrupted glucose homeostasis could play a […] causal role in AD pathogenesis. Although several prominent features of T2DM, including increased insulin resistance and decreased insulin production, are at the forefront of AD research (710), questions regarding the effects of elevated blood glucose independent of insulin resistance on AD pathology remain largely unexplored. In order to investigate the potential role of glucose metabolism in AD, we combined glucose clamps and in vivo microdialysis as a method to measure changes in brain metabolites in awake, freely moving mice during a hyperglycemic challenge. Our findings suggest that acute hyperglycemia raises interstitial fluid (ISF) Aβ levels by altering neuronal activity, which increases Aβ production. […] Since extracellular Aβ, and subsequently tau, aggregate in a concentration-dependent manner during the preclinical period of AD while individuals are cognitively normal (27), our findings suggest that repeated episodes of transient hyperglycemia, such as those found in T2DM, could both initiate and accelerate plaque accumulation. Thus, the correlation between hyperglycemia and increased ISF Aβ provides one potential explanation for the increased risk of AD and dementia in T2DM patients or individuals with elevated blood glucose levels. In addition, our work suggests that KATP channels within the hippocampus act as metabolic sensors and couple alterations in glucose concentrations with changes in electrical activity and extracellular Aβ levels. Not only does this offer one mechanistic explanation for the epidemiological link between T2DM and AD, but it also provides a potential therapeutic target for AD. Given that FDA-approved drugs already exist for the modulation of KATP channels and previous work demonstrates the benefits of sulfonylureas for treating animal models of AD (26), the identification of these channels as a link between hyperglycemia and AD pathology creates an avenue for translational research in AD.”

Why am I conflicted? Well, on the one hand it’s nice to know that they’re making progress in terms of figuring out why people get Alzheimer’s and potential therapeutic targets are being identified. On the other hand this – “our findings suggest that repeated episodes of transient hyperglycemia […] could both initiate and accelerate plaque accumulation” – is bad news if you’re a type 1 diabetic (I’d much rather have them identify risk factors to which I’m not exposed).

v. I recently noticed that Khan Academy has put up some videos about diabetes. From the few ones I’ve had a look at they don’t seem to contain much stuff I don’t already know so I’m not sure I’ll explore this playlist in any more detail, but I figured I might as well share a few of the videos here; the first one is about the pathophysiology of type 1 diabetes and the second one’s about diabetic nephropathy (kidney disease):

vi. On Being the Right Size, by J. B. S. Haldane. A neat little text. A few quotes:

“To the mouse and any smaller animal [gravity] presents practically no dangers. You can drop a mouse down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes. For the resistance presented to movement by the air is proportional to the surface of the moving object. Divide an animal’s length, breadth, and height each by ten; its weight is reduced to a thousandth, but its surface only to a hundredth. So the resistance to falling in the case of the small animal is relatively ten times greater than the driving force.

An insect, therefore, is not afraid of gravity; it can fall without danger, and can cling to the ceiling with remarkably little trouble. It can go in for elegant and fantastic forms of support like that of the daddy-longlegs. But there is a force which is as formidable to an insect as gravitation to a mammal. This is surface tension. A man coming out of a bath carries with him a film of water of about one-fiftieth of an inch in thickness. This weighs roughly a pound. A wet mouse has to carry about its own weight of water. A wet fly has to lift many times its own weight and, as everyone knows, a fly once wetted by water or any other liquid is in a very serious position indeed. An insect going for a drink is in as great danger as a man leaning out over a precipice in search of food. If it once falls into the grip of the surface tension of the water—that is to say, gets wet—it is likely to remain so until it drowns. A few insects, such as water-beetles, contrive to be unwettable; the majority keep well away from their drink by means of a long proboscis. […]

It is an elementary principle of aeronautics that the minimum speed needed to keep an aeroplane of a given shape in the air varies as the square root of its length. If its linear dimensions are increased four times, it must fly twice as fast. Now the power needed for the minimum speed increases more rapidly than the weight of the machine. So the larger aeroplane, which weighs sixty-four times as much as the smaller, needs one hundred and twenty-eight times its horsepower to keep up. Applying the same principle to the birds, we find that the limit to their size is soon reached. An angel whose muscles developed no more power weight for weight than those of an eagle or a pigeon would require a breast projecting for about four feet to house the muscles engaged in working its wings, while to economize in weight, its legs would have to be reduced to mere stilts. Actually a large bird such as an eagle or kite does not keep in the air mainly by moving its wings. It is generally to be seen soaring, that is to say balanced on a rising column of air. And even soaring becomes more and more difficult with increasing size. Were this not the case eagles might be as large as tigers and as formidable to man as hostile aeroplanes.

But it is time that we pass to some of the advantages of size. One of the most obvious is that it enables one to keep warm. All warmblooded animals at rest lose the same amount of heat from a unit area of skin, for which purpose they need a food-supply proportional to their surface and not to their weight. Five thousand mice weigh as much as a man. Their combined surface and food or oxygen consumption are about seventeen times a man’s. In fact a mouse eats about one quarter its own weight of food every day, which is mainly used in keeping it warm. For the same reason small animals cannot live in cold countries. In the arctic regions there are no reptiles or amphibians, and no small mammals. The smallest mammal in Spitzbergen is the fox. The small birds fly away in winter, while the insects die, though their eggs can survive six months or more of frost. The most successful mammals are bears, seals, and walruses.” [I think he’s a bit too categorical in his statements here and this topic is more contested today than it probably was when he wrote his text – see wikipedia’s coverage of Bergmann’s rule].

May 26, 2015 Posted by | Biology, Chess, Diabetes, Epidemiology, History, Khan Academy, Lectures, Medicine, Nephrology, Neurology, Wikipedia, Zoology | Leave a comment

An Introduction to Medical Diagnosis (4)

Here’s a previous post in the series covering this book. There’s a lot of stuff in these chapters, so the stuff below’s just some of the things I thought were interesting and worth being aware of. I’ve covered three chapters in this post: One about skin, nails and hair, one about the eye, and one about infectious and tropical diseases. I may post one more post about the book later on, but I’m not sure if I’ll do that or not at this point so this may be the last post in the series.

Okay, on to the book – skin, nails and hair (my coverage mostly deals with the skin):

“The skin is a highly specialized organ that covers the entire external surface of the body. Its various roles include protecting the body from trauma, infection and ultraviolet radiation. It provides waterproofing and is important for fluid and temperature regulation. It is essential for the detection of some sensory stimuli. […] Skin problems are extremely common and are responsible for 10–15 per cent of all consultations in general practice. […] Given that there are around 2000 dermatological conditions described, only common and important conditions, including some that might be especially relevant in the examination setting, can be covered here.”

Urticaria is characterized by the development of red dermal swellings known as weals […]. Scaling is not seen and the lesions are typically very itchy. The lesions result from the release of histamine from mast cells. An important clue to the diagnosis is that individual lesions come and go within 24 hours, although new lesions may be appearing at other sites. Another associated feature is dermographism: a firm scratch of the skin with an orange stick will produce a linear weal within a few minutes. Urticaria is common, estimated to affect up to 20 per cent of the population at some point in their lives.”

“Stevens–Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are thought to be two ends of a spectrum of the same condition. They are usually attributable to drug hypersensitivity, though a precipitant is not always identified. The latent period following initiation of the drug tends to be longer than seen with a classical maculopapular drug eruption. The disease is termed:
*SJS when 10 per cent or less of the body surface area epidermis detaches
*TEN when greater than 30 per cent detachment occurs.
Anything in between is designated SJS/TEN overlap. Following a prodrome of fever, an erythematous eruption develops. Macules, papules, or plaques may be seen. Some or all of the affected areas become vesicular or bullous, followed by sloughing off of the dead epidermis. This leads to potentially widespread denudation of skin. […] The affected skin is typically painful rather than itchy. […] The risk of death relates to the extent of epidermal loss and can exceed 30 per cent. […] A widespread ‘drug rash’ that is very painful should ring alarm bells.”

“Various skin problems arise in patients with diabetes mellitus. Bacterial and fungal infections are more common, due to impaired immunity. Vascular disease and neuropathy lead to ulceration on the feet, which can sometimes be very deep and there may be underlying osteomyelitis. Granuloma annulare […] and necrobiosis lipoidica have also been associated with diabetes, though many cases are seen in non-diabetic patients. The former produces smooth papules in an annular configuration, often coalescing into a ring. The latter usually occurs over the shins giving rise to yellow-brown discoloration, with marked atrophy and prominent telangiectasia. There is often an annular appearance, with a red or brown border. Acanthosis nigricans, velvety thickening of the flexural skin […], is seen with insulin resistance, with or without frank diabetes. […] Diabetic bullae are also occasionally seen and diabetic dermopathy produces hyperpigmented, atrophic plaques on the legs. The aetiology of these is unknown.”

“Malignant melanoma is one of the commonest cancers in young adults [and it] is responsible for almost three-quarters of skin cancer deaths, despite only accounting for around 4 per cent of skin cancers. Malignant melanoma can arise de novo or from a pre-existing naevus. Most are pigmented, but some are amelanotic. The most important prognostic factor for melanoma is the depth of the tumour when it is excised – Breslow’s thickness. As most malignant melanomas undergo a relatively prolonged radial (horizontal) growth phase prior to invading vertically, there is a window of opportunity for early detection and management, while the prognosis remains favourable. […] ‘Red flag’ findings […] in pigmented lesions are increasing size, darkening colour, irregular pigmentation, multiple colours within the same lesion, and itching or bleeding for no reason. […] In general, be suspicious if a lesion is rapidly changing.”

The eye:

“Most ocular surface diseases […] are bilateral, whereas most serious pathology (usually involving deeper structures) is unilateral […] Any significant reduction of vision suggests serious pathology [and] [s]udden visual loss always requires urgent investigation and referral to an ophthalmologist. […] Sudden loss of vision is commonly due to a vascular event. These may be vessel occlusions giving rise to ischaemia of vision-serving structures such as the retina, optic nerve or brain. Alternatively there may be vessel rupture and consequent bleeding which may either block transmission of light as in traumatic hyphaema (haemorrhage into the anterior chamber) and vitreous haemorrhage, or may distort the retina as in ‘wet’ age-related macular degeneration (AMD). […] Gradual loss of vision is commonly associated with degenerations or depositions. […] Transient loss of vision is commonly due to temporary or subcritical vascular insufficiency […] Persistent loss of vision suggests structural changes […] or irreversible damage”.

There are a lot of questions one might ask here, and I actually found it interesting to know how much can be learned simply by asking some questions which might help narrow things down – the above are just examples of variables to consider, and there are others as well, e.g. whether or not there is pain (“Painful blurring of vision is most commonly associated with diseases at the front of the eye”, whereas “Painless loss of vision usually arises from problems in the posterior part of the eye”), whether there’s discharge, just how the vision is affected (a blind spot, peripheral field loss, floaters, double vision, …), etc.

“Ptosis (i.e. drooping lid) and a dilated pupil suggest an ipsilateral cranial nerve III palsy. This is a neuro-ophthalmic emergency since it may represent an aneurysm of the posterior communicating artery. […] In such cases the palsy may be the only warning of impending aneurysmal rupture with subsequent subarachnoid haemorrhage. One helpful feature that warns that a cranial nerve III palsy may be compressive is pupil involvement (i.e. a dilated pupil).”

“Although some degree of cataract (loss of transparency of the lens) is almost universal in those >65 years of age, it is only a problem when it is restricting the patient’s activity. It is most commonly due to ageing, but it may be associated with ocular disease (e.g. uveitis), systemic disease (e.g. diabetes), drugs (e.g. systemic corticosteroids) or it may be inherited. It is the commonest cause of treatable blindness worldwide. […] Glaucoma describes a group of eye conditions characterized by a progressive optic neuropathy and visual field loss, in which the intraocular pressure is sufficiently raised to impair normal optic nerve function. Glaucoma may present insidiously or acutely. In the more common primary open angle glaucoma, there is an asymptomatic sustained elevation in intraocular pressure which may cause gradual unnoticed loss of visual field over years, and is a significant cause of blindness worldwide. […] Primary open angle glaucoma is asymptomatic until sufficiently advanced for field loss to be noticeable to the patient. […] Acute angle closure glaucoma is an ophthalmic emergency in which closure of the drainage angle causes a sudden symptomatic elevation of intraocular pressure which may rapidly damage the optic nerve.”

“Age-related macular degeneration is the commonest cause of blindness in the older population (>65 years) in the Western world. Since it is primarily the macula […] that is affected, patients retain their peripheral vision and with it a variable level of independence. There are two forms: ‘dry’ AMD accounts for 90 per cent of cases and the more dramatic ‘wet’ (also known as neovascular) AMD accounts for 10 per cent. […] Treatments for dry AMD do not alter the course of the disease but revolve around optimizing the patient’s remaining vision, such as using magnifiers. […] Treatments for wet AMD seek to reverse the neovascular process”.

“Diabetes is the commonest cause of blindness in the younger population (<65 years) in the Western world. Diabetic retinopathy is a microvascular disease of the retinal circulation. In both type 1 and type 2 diabetes glycaemic control and blood pressure should be optimized to reduce progression. Progression of retinopathy to the proliferative stage is most commonly seen in type 1 diabetes, whereas maculopathy is more commonly a feature of type 2 diabetes. […] Symptoms
*Bilateral. *Usually asymptomatic until either maculopathy or vitreous haemorrhage. [This is part of why screening programs for diabetic eye disease are so common – the first sign of eye disease may well be catastrophic and irreversible vision loss, despite the fact that the disease process may take years or decades to develop to that point] *Gradual loss of vision – suggests diabetic maculopathy (especially if distortion) or cataract. *Sudden loss of vision – most commonly vitreous haemorrhage secondary to proliferative diabetic retinopathy.”

Recap of some key points made in the chapter:
“*For uncomfortable/red eyes, grittiness, itchiness or a foreign body sensation usually indicate ocular surface problems such as conjunctivitis.
*Severe ‘aching’ eye pain suggests serious eye pathology such as acute angle closure glaucoma or scleritis.  *Photophobia is most commonly seen with acute anterior uveitis or corneal disease (ulcers or trauma). [it’s also common in migraine]
*Sudden loss of vision is usually due to a vascular event (e.g. retinal vessel occlusions, anterior ischaemic optic neuropathy, ‘wet’ AMD).
*Gradual loss of vision is common in the ageing population. It is frequently due to cataract […], primary open angle glaucoma (peripheral field loss) or ‘dry’ AMD (central field loss).
*Recent-onset flashes and floaters should be presumed to be retinal tear/detachment.
*Double vision may be monocular (both images from the same eye) or binocular (different images from each eye). Binocular double vision is serious, commonly arising from a cranial nerve III, IV or VI palsy. […]
the following presentations are sufficiently serious to warrant urgent referral to an ophthalmologist: sudden loss of vision, severe ‘aching’ eye pain, new-onset flashes and floaters, [and] new-onset binocular diplopia.”

Infectious and tropical diseases:

“Patients with infection (and inflammatory conditions or, less commonly, malignancy) usually report fever […] Whatever the cause, body temperature generally rises in the evening and falls during the night […] Fever is often lower or absent in the morning […]. A sensation of ‘feeling hot’ or ‘feeling cold’ is unreliable – healthy individuals often feel these sensations, as may those with menopausal flushing, thyrotoxicosis, stress, panic, or migraine. The height and duration of fever are important. Rigors (chills or shivering, often uncontrollable and lasting for 20–30 minutes) are highly significant, and so is a documented temperature over 37.5 °C taken with a reliable oral thermometer. Drenching sweats are also highly significant. Rigors generally indicate serious bacterial infections […] or malaria. An oral temperature >39 °C has the same significance as rigors. Rigors generally do not occur in mild viral infections […] malignancy, connective tissue diseases, tuberculosis and other chronic infections. […] Anyone with fever lasting longer than a week should have lost weight – if a patient reports a prolonged fever but no weight loss, the ‘fever’ usually turns out to be of no consequence. […] untouched meals indicate ongoing illness; return of appetite is a reliable sign of recovery.”

“Bacterial infections are the most common cause of sepsis, but other serious infections (e.g. falciparum malaria) or inflammatory states (e.g. pancreatitis, pre-eclamptic toxaemia, burns) can cause the same features. Below are listed the indicators of sepsis – the more abnormal the result, the more severe is the patient’s condition.
Temperature
*Check if it is above 38 °C or below 36 °C.
*Simple viral infections seldom exceed 39 °C.
*Temperatures (from any cause) are generally higher in the evening than in the early morning.
*As noted above, rigors (uncontrollable shivering) are important indicators of severe bacterial infection or malaria. […] A heart rate greater than 90 beats/min is abnormal, and in severe sepsis a pulse of 140/min is not unusual. […] Peripheries (fingers, toes, nose) are often markedly cooler than central skin (trunk, forehead) with prolonged capillary refill time […] Blood pressure (BP) is low in the supine position (systolic BP <90 mmHg) and falls further when the patient is repositioned upright. In septic shock sometimes the BP is unrecordable on standing, and the patient may faint when they are helped to stand up […] The first sign [of respiratory disturbance] is a respiratory rate greater than 20 breaths/min. This is often a combination of two abnormalities: hypoxia caused by intrapulmonary shunts, and lactic acidosis. […] in hypoxia, the respiratory pattern is normal but rapid. Acidotic breathing has a deep, sighing character (also known as Kussmaul’s respiration). […] Also called toxic encephalopathy or delirium, confusion or drowsiness is often present in sepsis. […] Sepsis is always severe when it is accompanied by organ dysfunction. Septic shock is defined as severe sepsis with hypotension despite adequate fluid replacement.”

“Involuntary neck stiffness (‘nuchal rigidity’) is a characteristic sign of meningitis […] Patients with meningitis or subarachnoid haemorrhage characteristically lie still and do not move the head voluntarily. Patients who complain about a stiff neck are often worried about meningitis; patients with meningitis generally complain of a sore head, not a sore neck – thus neck stiffness is a sign, not a symptom, of meningitis.”

“General practitioners are generally correct when they say an infection is ‘a virus’, but the doctor needs to make an accurate assessment to be sure of not missing a serious bacterial infection masquerading as ‘flu’. […]
*Influenza is highly infectious, so friends, family, or colleagues should also be affected at the same time – the incubation period is short (1–3 days). If there are no other cases, question the diagnosis.
*The onset of viraemic symptoms is abrupt and often quite severe, with chills, headache, and myalgia. There may be mild rigors on the first day, but these are not sustained.
*As the next few days pass, the fever improves each day, and by day 3 the fever is settling or absent. A fever that continues for more than 3 days is not uncomplicated ’flu, and nor is an illness with rigors after the first day.
*As the viraemia subsides, so the upper respiratory symptoms become prominent […] The patient experiences a combination of: rasping sore throat, dry cough, hoarseness, coryza, red eyes, congested sinuses. These persist for a long time (10 days is not unusual) and the patient feels ‘miserable’ but the fever is no longer prominent.”

“Several infections cause a similar picture to ‘glandular fever’. The commonest is EBV [Epstein–Barr Virus], with cytomegalovirus (CMV) a close second; HIV seroconversion may look clinically identical, and acute toxoplasmosis similar (except for the lack of sore throat). Glandular fever in the USA is called ‘infectious mononucleosis’ […] The illness starts with viraemic symptoms of fever (without marked rigors), myalgia, lassitude, and anorexia. A sore throat is characteristic, and the urine often darkens (indicating liver involvement). […] Be very alert for any sign of stridor, or if the tonsils meet in the middle or are threatening to obstruct (a clue is that the patient is unable to swallow their saliva and is drooling or spitting it out). If there are any of these signs of upper airway obstruction, give steroids, intravenous fluids, and call the ENT surgeons urgently – fatal obstruction occasionally occurs in the middle of the night. […] Be very alert for a painful or tender spleen, or any signs of peritonism. In glandular fever the spleen may rupture spontaneously; it is rare, but tragic. It usually begins as a subcapsular haematoma, with pain and tenderness in the left upper quadrant. A secondary rupture through the capsule then occurs at a later date, and this is often rapidly fatal.”

April 7, 2015 Posted by | Books, Cancer/oncology, Diabetes, Infectious disease, Medicine, Neurology | Leave a comment

An Introduction to Medical Diagnosis (II)

Here’s my first post about the book. In this post I’ll cover two more of the individual systems chapters – the first of the chapters I’ll talk about is the one about the renal system (kidneys). Some key symptoms which may suggest renal pathology are disorders of micturition (urination), disorders of urine volume, changes in urine composition, loin pain, oedema, and hypertension. Disorders of micturition can relate to frequency, poor urinary stream (typically caused by outflow obstructions) and dysuria (pain on micturition). There are 19 different causes of frequency mentioned in a table in the chapter, so there are a lot of possible causes. Volume changes may be termed polyuria (increase in volume), oliguria (decrease-), or anuria (total loss of urine output – this is bad); it’s important to note that frequency does not necessarily imply polyuria. Blood in the urine is called haematuria, a symptom which will often cause people to seek medical attention – for good reason: “Any patient above the age of 40 years with haematuria (visible or invisible) requires urgent evaluation by a urologist to look for malignant disease of the urinary tract.” It should however be noted that red/brown urine doesn’t necessarily indicate haematuria – other common causes are drugs and vegetable dyes – and relatedly it should be mentioned that blood in the urine may not be visible (haematuria is sometimes caught as an incidental finding by dip-stick analysis of the urine). When blood is present in the urine at the start of micturition only it usually indicates urethral bleeding, whereas bleeding towards the end of micturition is indicative of bladder/prostate bleeding. In the context of kidney disease pain patterns are inconsistent, but when there’s pain it’s usually due to renal tract inflammation or obstruction (e.g. due to a kidney stone). Cancer need not cause pain: “The cardinal feature of transitional cell carcinoma of the urinary tract is painless haematuria”, which may or may not be visible to the naked eye. In bladder cancer ‘local’ symptoms such as frequency and nocturia present before systemic symptoms such as weight loss, and the latter symptoms usually present late. Risk factors include smoking, occupational exposure to hydrocarbons, ionizing radiation (e.g. previous cancer treatment), prolonged immunosuppression, and bladder stones.

There are a number of inherited renal diseases, as well as a huge number of medical conditions associated with renal disease (18 of them are listed in the chapter). Aside from specific medical conditions a large number of drugs may also impact kidney function and the risk of developing renal disease. Pregnancy is a risk factor. Dietary factors may be important in some cases; for example excessive salt intake may lead to hypertension, as may alcohol, and hypertension is bad for the kidneys. Another example would be inadequate fluid intake or high intake of animal protein, both of which may promote lithiasis (stone formation). Tobacco is a significant risk factor for the development and progression of kidney disease. Of the many causes of kidney failure, diabetic renal disease is the most common cause of end-stage renal disease (-ESRD) in the Western world, according to the book accounting for 20-50% of new patients with end-stage renal disease (presumably the estimate is so broad-banded due to major cross-country differences). Another important cause is autosomal dominant polycystic kidney disease (ADPKD), which make up 10 per cent of patients with ESRD. Women have urinary tract infections (-UTI) much more often than men, and 50-60 per cent of women have at least one UTI during their lives. In males the risk has been estimated to be 5/10.000/year. It’s noted in the next chapter of the book that “Urinary tract infections (UTIs) are common in women, but uncommon in men under 50 years old”, but that “[o]lder men may get UTIs secondary to bladder outflow obstruction from prostatic hypertrophy”. I won’t talk much about that chapter, about the genitourinary system, as I’ve talked quite a bit about these sorts of things before when covering Holmes et al., e.g. here and here, but one other important quote is probably worth including here as well: “Seventy-five per cent of people infected with HSV [herpes simplex virus] are not aware that they have genital herpes either because their symptoms are very mild/absent or because the symptoms have been assumed to be due to something else (most commonly thrush).”

The other main chapter I’ll cover here is the chapter about the nervous system. I liked the way the author starts out the chapter – here’s a quote from the beginning of the chapter: “Inexperienced clinicians often order sophisticated (and expensive!) investigations hoping that the diagnosis may be revealed, but sadly this rarely happens. Many investigations are relatively sensitive but not necessarily disease specific”. Later on he also notes that it is his opinion that: “Electroencephalograms (EEGs) are grossly overordered. They should not be used as a diagnostic tool in epilepsy as they are relatively non-specific and non-sensitive.” I liked this stuff in part because I’m the sort of person who cares about cost-effectiveness, but also because Eysenck and Keane’s Cognitive Psychology text, part of which I read last December, contained some reasonably detailed coverage of various imaging methods used in these contexts and what you can and cannot use them for; and I think it’s highly likely that the author of the chapter is right. I may go into much more details about this kind of stuff later if I decide to cover E&K’s book, but I won’t talk about it here. One related observation worth including here is however that in the context of a seizure, something as ‘low-tech’ as an available eye-witness is often crucial (was there jerking? pallor? gaze aversion?) to make a diagnosis and distinguish between an epileptic seizure and a cardiovascular syncope (the most common diagnostic dilemma here).

Headaches are common. It’s useful to know that whereas an acute headache may be a sign of sinister pathology, chronic headaches rarely are. Acute headaches may be almost instantaneous (hyperacute), or they may develop over hours to days. Instantaneous headache may be (but of course needn’t be) due to life-threatening conditions such as subarachnoid haemorrhage, venous sinus thrombosis, cerebral haemorrhage, and phaeochromocytoma, all of which may present that way. The combination of neck stiffness and photophobia (together with headache) is called meningism and this is something that requires urgent investigation, as it may be due to meningitis or encephalitis. Muscle weakness is a common neurological symptom, and here it’s important to note that hyperacute limb weakness is usually caused by a stroke, and is most commonly unilateral (i.e. affecting e.g. only one arm or leg, rather than both), whereas bilateral weakness is a marker of spinal cord disease. Sensory symptoms may be either ‘positive’ (e.g. tingling, dysaesthesia) or negative (numbness); stroke usually causes negative symptoms, whereas various genetic or acquired disorders may also present with ‘positive’ symptoms as well. “Neuropathic pain (cf diabetes) is often lower limb predominant and described as burning, stinging or throbbing.” Relatedly: “Diabetes is the commonest cause of neuropathy in the UK; distal predominantly sensory neuropathy, diabetic amyotrophy (pain and wasting in femoral distribution), nerve entrapments (carpal tunnel syndrome), cranial neuropathy and autonomic neuropathy are relatively common complications.” As for the aforementioned strokes, they’re sometimes (in 15 per cent of cases, according to the book) preceded by a TIA (a transient ischaemic attack), a sort of ‘mini-stroke’ which causes a reversible neurological deficit lasting less than 24 hours (‘in practice much shorter duration’). A recent TIA puts you in high immediate risk of stroke, which is probably useful to know – for more details, see this link.

The nervous system deals with a lot of stuff, so a lot of things can go wrong. Autonomic nervous system disorders may cause symptoms/problems such as: sphincter disturbances (e.g. incontinence), change in sweating patterns, photophobia (when the pupil is affected), night blindness, orthostatic hypotension, dry mouth, dry eyes, erectile/ejaculatory failure, and vomiting. Specific nerves doing specific things can cause specific symptoms when they stop working the way they’re supposed to, and these sorts of symptoms are very far from limited to ‘people being unable to move their arms or legs’; neurological problems can also cause you to e.g. go blind or deaf. The distinction between monolateral (‘vascular’) and bilateral (‘neurological’) symptoms and how this distinction relate to the underlying medical cause seems to apply not only to major limbs, but also to other areas of the body – for example if you’re experiencing vision loss in both eyes it’s more often a neurological problem, whereas problems caused by retinal pathology tend to cause unilateral symptoms. On a related note, in elderly people monocular loss of vision can be a harbinger of stroke. They mention in this chapter that neurological dysphagia (difficulty swallowing) may affect liquids first, whereas a mechanical obstruction (e.g. due to a tumour) will preferentially affect solids (I mentioned this in my last post about the book). “The duration of anterograde amnesia is an extremely useful indicator of the severity of head injury.” In the last part of the chapter the author talks about various specific conditions causing neurological problems, such as Parkinson’s disease, Motor Neuron Disease, Multiple Sclerosis, Myasthenia gravis, and Guillain–Barré syndrome – I won’t cover these in any detail as the book only covers them very briefly (you can google them if you’re curious).

February 6, 2015 Posted by | Books, Epidemiology, Medicine, Nephrology, Neurology | Leave a comment

Delusion and Self-Deception – Affective and Motivational Influences on Belief Formation (II)

[A brief note before moving on to the book review: I was just notified by wordpress when publishing this post that I have now posted 2001 posts on this blog. It would of course have made more sense to add a remark in the post which came before this one, but I didn’t notice and I had no idea I was that close to the 2000-mark. I don’t know if the number is correct; it somehow seems ‘too high’ to me, but I’m not going to count the posts in order to figure out if the number is correct. Even if I did try to do that I know that I have deleted a lot of posts over the years, so there are a lot fewer posts than that available in the archives, and so I wouldn’t be able to tell anyway from the information which is available to me now. According to the summary information displayed on my dashboard right now, there are 1304 posts in the archives. Anyway, I thought I should mention this here.]

I finished the book.

There were a couple of really nice chapters in the first half, but there was a lot of not-great stuff as well; the average quality and the variance of the quality of the material included in the second half was reasonably similar. Some parts of the second half were quite helpful in terms of making better sense of some of the stuff the poorer chapters in the first part dealt with. I gave the book two stars on goodreads. I must admit that I think the editor might have done a better job; I was very annoyed by the inclusion of multiple articles in the first part of the book which either completely neglected to define terms used in the text, or described them poorly. A couple of times throughout the book I came across an explanation of a term/distinction which had been used in multiple previous chapters where I’d earlier on been sort of semi-guessing what they meant when they talked about this stuff, and suddenly I realized that it was really quite easy to explain, only the previous authors hadn’t done that (/been able to do that?). You could argue that part of the problem is that some of the contributions were not well written and that you can’t blame the editors for that, but to me it seems problematic to include in a book like this some chapters reasonably early in the text which assume you know all about X, and then multiple chapters later you include in the work a chapter written by someone who (more reasonably) assumes that people may perhaps have no clue what X refers to – it might have been smart to include the latter chapter a bit sooner in the coverage..

The book is published by Psychology Press, but some chapters are written by philosophers rather than psychologists. Although not all of the coverage is purely conceptual, there’s a lot of that stuff in this book and the amount of empirical content is not very impressive, at least not if you don’t think much of elaborate descriptions of anecdotes and studies conducted on 6 people or something like that; I recall this having been a big issue for me previously when looking at some related neuroscience (there’s some neuroscience in the book, as also indicated in the previous post), some of which is occasionally mentioned in the work (specifically the research done by Ramachandran & Sacks).

Part of the low rating on my part is surely due to unmet expectations; I’d expected the book to cover in some detail what might be termed ‘common self-deception’ in ordinary people; the type of self-deception normal people engage in all the time. There’s almost none of that in the book, though there are a few comments on that topic here and there. Most book chapters focus mainly on people with specific delusions – especially the Capgras delusion, there are a lot of chapters talking about that one – and then talk about what’s the best way to model this disorder; in the context of the various (conceptual) models proposed, they then occasionally include considerations as to whether such patients are best thought of as self-deceiving or not, and what we might actually mean by this. Although this is interesting enough, I didn’t pick up the book because I thought that was what was inside it. That some expectations were unmet was not the only reason why I mentally subtracted a bit from the overall rating; I have a perhaps irrational tendency to become annoyed when people writing books like these don’t seem to know (relevant) stuff I do, and in this case an author made the ‘mistake’ of talking about Othello syndrome (basically: ‘delusional jealousy’) without seeming to be at all familiar with relevant ethological research such as what’s included in texts like this one. I thought the lack of familiarity with this field meant that the theoretical notions included in that part of the coverage completely overlooked some really big variables and meaningful approaches to how to conceptualize this syndrome. In all fairness it should be noted that another author elsewhere in the book actually does seem familiar with at least some parts of this research and in fact explicitly refers to it in the text.

Although there’s a lot of what might be termed ‘conceptual coverage’ in the book it’s not like there isn’t some empirical stuff as well; to take an example, the book has a chapter called ‘Emotion, Cognition, and Belief – Findings From Cognitive Neuroscience’. To the extent that the coverage is empirical it’s mostly asking questions such as what happens to/in the brains of people with or without specific brain lesions known to be related to specific delusions, and how we can know this/have tested this. This is interesting enough; there’s some work presented suggesting for example that the risk of development of a specific type of quite common stroke-related delusional belief where the patient denies that he’s suffering from paralysis – even if he obviously can’t move his arm or leg – is related to which part of the brain is damaged (see below).

I’ve added some observations from a few of the chapters I did not cover in the first post below. Although I may sound critical in my comments above, I should note that there was a reason why I finished the book instead of giving up on it; there were quite a few interesting observations along the way, many of which I found myself unable to include in the coverage of the book here for various reasons.

“Until recently, many delusions were widely regarded as having a motivational psychogenesis. That is, delusions were viewed as being motivated and their formation and maintenance seen as attributable to the psychological benefits they provided to deluded individuals. […] This explicitly motivational formulation, which explains a delusory belief in terms of the psychological benefits it confers, is consistent with a long tradition in psychology, the psychodynamic tradition. […] The key notion in psychoanalytic [/…-dynamic] accounts is that delusions are viewed as having a palliative function; they represent an attempt (however misguided) to relieve pain, tension, and distress. […] Motivational accounts of delusions can be generally distinguished from another major explanatory class — that involving the notion of defect or deficit […] Theories in this second class view delusions as the consequence of fundamental cognitive or perceptual anomalies ranging from complete breakdowns in certain crucial elements of cognitive–perceptual machinery […] to milder dysfunctions involving the distorted operation of particular processes […] There is little doubt that the edifice of psychodynamic thought is replete with theorizing that is at once outrageously presumptive and outlandishly speculative. [I liked this sentence… ] […] For the purposes of this chapter, [however,] the core insight is that motives (conscious or otherwise) are important causal forces doxastically (doxastic = of or relating to belief). Psychoanalysis, of course, contains other conceptual elements and theoretical postulates that we might not want to endorse or consider”

“Self-deception is a notoriously slippery notion that has eluded definitional consensus. Sackeim and Gur (1978) provided what is arguably the most widely accepted characterization in the psychological literature, claiming that self-deception consists in an individual holding two contradictory beliefs simultaneously; the individual, moreover, is aware of only one of these beliefs and is motivated to remain unaware of the other. This kind of conceptualization courts philosophical controversy in that it entails what are known as the “static” and “dynamic” paradoxes of self-deception […]. The static paradox consists in a self-deceived person being simultaneously in two contradictory states: the states of believing and disbelieving a particular proposition. The dynamic paradox arises out of the fact that in order for a person to engage in self-deception, he or she must know what he or she is doing; yet, in order for the project to work, he or she must not know what he or she is doing. Mele (this volume) offers a “deflationary” account of self-deception that skirts these paradoxes. In his account, self-deception occurs when a “desire that p” contributes to a “belief that p.” Mele outlines how this can happen unparadoxically (via such phenomena as negative and positive misinterpretation, selective focusing, and selective evidence-gathering). Regarding self-deception’s relationship to the notion of delusion, the two terms have been variously used as synonyms […], as qualitatively similar concepts that differ quantitatively […], and as quite distinct, if overlapping, concepts […] We argue that it is indeed useful to view delusion and self-deception as distinct concepts that intersect or overlap. […] Essentially, we view delusion as connoting both a dearth of evidential justification and an element of day-to-day dysfunction. A person is deluded when he or she has come to hold a particular belief with a degree of firmness that is utterly unwarranted by the evidence at hand and that jeopardizes their everyday functioning.[13] [Note that at the time they wrote the book, official diagnostic manuals such as the DSM-IV did not include ‘everyday functioning’ as a diagnostic criteria; so the criteria proposed are in some sense more restrictive than the ‘official ones’ applied at that time. I have no idea what the current criteria are, but I also don’t much care – US]. Self-deception, on the other hand, we view (with Mele) as paradigmatically motivated. Self-deceptive beliefs may or may not contradict reality, and they may or may not disrupt daily living. What is important is that they are not formed out of a wholly dispassionate quest for the truth, but rather are somehow influenced or biased by the prevailing motivational state of the individual concerned. […] Theoretically, at least, each may occur in isolation. Thus, some delusions may arise without self-deception via processes that are not remotely motivated. […] Conversely, certain instances of self-deception may not sufficiently disrupt functioning to warrant the label delusion. […] [Common] self-serving tendencies do not ordinarily merit usage of the term delusion.”

“A two-factor account [of delusions] offers distinct answers to […] two questions in terms of two departures from normality. The first factor explains why the false proposition seemed a somewhat salient and credible hypothesis or why it was initially adopted as a belief. The second factor explains why the proposition is not subsequently rejected.”

Another author in the book framed the disctinction as being one between the content of the delusion and the maintenance of the delusion. The second factor has been proposed to relate to belief evaluation mechanisms in some way or other, but most authors aren’t very specific when talking about this stuff and most of that coverage seemed to me very speculative. I won’t talk much more about these accounts/conceptual models here, but I will note that they spend a lot of pages talking about the two-factor accounts in the book. It seems to be difficult to explain the content and the maintenance of delusions, applying the terminology proposed in the other chapter, using only a single factor, which is why such models have been developed:

“The argument for a second factor in the etiology of delusions is that, both normally and normatively, the first factor is not sufficient to explain the delusion. The first factor prompts an apparently salient and somewhat credible hypothesis or candidate belief but the hypothesis or candidate belief normally could be, and normatively should be, rejected. Even if the first factor explains why the hypothesis is initially adopted as a belief, it does not explain the delusion because it does not explain why the belief is tenaciously maintained […] We need a second factor to answer the question of why the patient does not reject the belief.”

It should be noted in the context of the distinction between deficit accounts and motivational accounts above that two-factor accounts do not include motivational factors, being purely deficit accounts, although one author in the book suggests that it might make sense to try to combine the models (a thought that also occurred to me while reading the book). Most accounts of this stuff were as mentioned speculative, but in one context – anosognosia in stroke victims – it seems there’s actually some relevant knowledge and data:

“Patients with anosognosia fail to acknowledge, or even outright deny, their impairment or illness […] In this chapter, we shall be concerned with anosognosia for hemiplegia (paralysis of one side of the body) or, more generally, for motor impairments. A patient whose arm or leg is paralyzed or weak following a stroke may deny the weakness in response to questions like, “Is there anything wrong with your arm or leg? Is it weak, paralyzed or numb?” […], and they may continue to deny the impairment even when it has been demonstrated. For example, the examiner may ask the patient to raise both arms and then demonstrate to the patient that one arm is not raised as high as the other. […] According to the neuropsychological version of the two-factor theory, the second factor, which does its work after the generation of the delusional hypothesis, candidate belief, or initially adopted belief, is a deficit in the cognitive mechanisms responsible for belief evaluation and revision. No very detailed account of this second deficit has yet been provided […] Although the second deficit is poorly specified in terms of cognitive function, there are some suggestions about its neural basis. For example, following a right-hemisphere stroke, patients may deny ownership of their paralyzed left-side limbs […]. The fact that patients with somatoparaphrenia [denial of ownership: The patient may basically for example believe that ‘this is not my arm’, even if it is in fact his arm…US] generally have intact left hemispheres suggests that the second deficit results from right-hemisphere damage, and other evidence supports this suggestion.[4] […] Recent studies of patients in the first 10 days following a stroke suggest a rate of occurrence for anosognosia of 17–21% […] and 21–42% for right-hemisphere patients […] Studies also suggest a rate of occurrence for unilateral neglect [“Patients with unilateral neglect fail to respond to stimuli presented on the side opposite to their lesion”] of 23% […] and 32–42% among right-hemisphere patients [These kinds of delusional beliefs are as illustrated by these numbers not absurd notions which pop up in one in a million patients; they are really common in the stroke contextIt should be mentioned here that in most patients the delusional beliefs seem to resolve over time: “by comparison with anosognosia in the first few days following a stroke, persisting anosognosia is relatively rare.”]

“One way to reinterpret delusional subjects is to say that we’ve misidentified the content of the problematic belief. For example, we might say that rather than believing that his wife has been replaced by an impostor, the victim of the Capgras delusion believes that it is, in some respects, as if his wife has been replaced by an impostor. Another is to say that we’ve misidentified the attitude that the delusional subject bears to the content of the delusion. For example, Gregory Currie and coauthors have suggested that rather than believing that his wife has been replaced by an impostor, we should say that the victim of the Capgras delusion merely imagines that his wife has been replaced by an impostor. […] I want to suggest that […] we ought to say that delusional subjects don’t straightforwardly believe the contents of their delusions or straightforwardly imagine them. Instead, they bear some intermediate attitude — we might call it “bimagination” — with some of the distinctive features of believing and some of the distinctive features of imagining. […] People with inconsistent beliefs don’t just infer everything, and it often happens that they find themselves failing to believe some of the consequences of what they believe. […] Closure takes cognitive work, and some of the consequences of our beliefs are easier to spot than others. Here is an explanation of this fact: Not every belief-type representation is equally tied to every other. There are coordination constraints between belief-type representations. These sorts of connections encourage consistency among belief-type representations and the elaboration of belief-type representations or the production of new ones that represent the consequences of things represented in our various beliefs. But these connections are not equally strong everywhere. Some of our beliefs are very closely tied to one another, so the elimination of inconsistency and drawing of inferences comes easily or automatically. However, there are also pairs of belief-type representations that are not so closely tied to one another, where elimination of inconsistency and drawing of inferences is difficult and/or unlikely. […] the belief role isn’t monolithic. Within belief, there’s variation in the sort of behavior-guiding role that’s played by different beliefs, and there’s variation in the sort of inference-generating role that’s played by different beliefs. […]

Here, I think, is the moral: The belief role and the imagination role are a lot more complicated and a lot less unified than we might have thought. It’s not just a matter of a given representation being hooked up like a belief or hooked up like an imagining. A given belief-type representation will have a whole range of different connections to different behavior-planning mechanisms (or to different bits of the one mechanism, or different kinds of connections to the same bit of the same mechanism, or…) and a whole range of different kinds of connections to different representations of various types. There are no necessary connections between these various connections; it’s not the case that anything that’s got one element of a certain package has also got to have all of the rest because we see a variety of mix-and-match patterns even within belief. No belief-type representation plays the whole stereotypical belief role — regulating all behavior all the time and being equally and perfectly coordinated with all of our other beliefs. The different bits of the stereotypical role — for example, regulating this bit of behavior in these circumstances and combining with these sorts of beliefs to generate inference — are separable. Thus, there seems to be no principled reason to think that we can’t get a spectrum of cases, from clear, totally non-belief-like imaginings to clear, full-blooded, paradigmatic beliefs, with intermediate, hard-to-classify states in the middle.”

“If we think that a certain sort of evidence responsiveness is essential to belief, then, in many cases, we’ll be reluctant to say that delusional subjects genuinely believe the contents of their delusions. Thus, we’ll be uncomfortable with characterizing delusions as genuine beliefs. Another respect in which delusions are puzzling, which makes categorizing delusions as beliefs problematic, is that delusions, when compared to other beliefs, seem to have an importantly circumscribed role in subjects’ cognitive economies. […] The first way in which the cognitive role of delusions is circumscribed relative to that of paradigmatic beliefs is inferential. Delusional subjects often do not draw the sorts of inferences that we might expect from someone who believed the content of his or her delusion. A subject with the Capgras delusion, for example, who believes that his wife has been replaced by a duplicate, is likely not to adopt an overall worldview according to which it makes sense that his spouse should have been replaced by an impostor. […] Another respect in which the role of delusional beliefs is circumscribed is behavioral. Delusional subjects fail, in important ways, to act in ways that we would expect from someone who genuinely believed the things that he or she professed to believe. […] Finally, the delusional belief’s role in subjects’ emotional lives seems to be circumscribed as well. Subjects often do not seem to experience the sorts of affective responses that we would expect from someone who believed that, for example, his or her spouse had been replaced by an impostor. […] Imagining displays the right kind of evidence independence. In order to imagine that P, I needn’t have any evidence that P. Further, getting evidence that not-P or noticing that I already had such evidence needn’t interfere at all with my continuing to imagine that P. […] Classifying delusions as straightforward, paradigmatic cases of belief is problematic because it predicts that delusions ought not to display the sorts of circumscription and evidence independence that they in fact display. Classifying them as straightforward, paradigmatic cases of imagination is [however also] problematic because it predicts that they should display more circumscription and evidence independence than they in fact display. What would be nice would be to be able to say that the attitude is something in between paradigmatic belief and paradigmatic imagination — that delusional subjects are in states that play a role in their cognitive economies that is in some respects like that of a standard-issue, stereotypical belief that P and in other respects like that of a standard-issue, stereotypical imagining that P.”

“Some cases of self-deception seem to display the same sort of peculiar circumscription and insensitivity to evidence that’s characteristic of delusions. In these cases, we may have the same sort of reluctance to say that self-deceivers genuinely believe that the relevant proposition is true; however, it also doesn’t seem right to say that they merely desire that it’s true, either. Instead, they seem to be in an intermediate state between belief and desire. […] This would allow for the self-deceiver’s “belief” to be insensitive to evidence for its falsity in the same way as a desire, and yet to play some part of the behavior-guiding role of belief. It would also allow us to account for cases in which the self-deceiver’s “belief” has an impoverished behavior-guiding and inferential role, as seems to be the case sometimes. I don’t want to suggest that this is the right account of self-deception in general. I suspect that self-deception is a many-splendored thing and that there won’t be any single, unified account of self-deception in general to be found. Instead, I want to suggest that this sort of intermediate-state account is the right way to describe what’s going on in some restricted class of cases that might plausibly fall under the heading of “self-deception”—the ones that display the same peculiar sort of evidence independence and circumscription that we see in delusions.
There are, broadly speaking, two sorts of accounts of the origin of intermediate attitudes. […] In the first account, the representations are peculiar from the get-go: Something goes wrong in the original construction of the representation, so it winds up with a nonstandard role in the subject’s cognitive economy. In the second sort of account, the problematic representations start off with a fairly standard functional role and then they drift into some intermediate area. […] The self-deception account […] fits best with this second kind of origin. The most plausible sort of story seems to be one on which some representations start life as desires, but eventually acquire some aspects of the functional role of a belief.”

December 5, 2014 Posted by | Books, Medicine, Neurology, Psychology | Leave a comment

Wikipedia articles of interest

i. Trade and use of saffron.

Saffron has been a key seasoning, fragrance, dye, and medicine for over three millennia.[1] One of the world’s most expensive spices by weight,[2] saffron consists of stigmas plucked from the vegetatively propagated and sterile Crocus sativus, known popularly as the saffron crocus. The resulting dried “threads”[N 1] are distinguished by their bitter taste, hay-like fragrance, and slight metallic notes. The saffron crocus is unknown in the wild; its most likely precursor, Crocus cartwrightianus, originated in Crete or Central Asia;[3] The saffron crocus is native to Southwest Asia and was first cultivated in what is now Greece.[4][5][6]

From antiquity to modern times the history of saffron is full of applications in food, drink, and traditional herbal medicine: from Africa and Asia to Europe and the Americas the brilliant red threads were—and are—prized in baking, curries, and liquor. It coloured textiles and other items and often helped confer the social standing of political elites and religious adepts. Ancient peoples believed saffron could be used to treat stomach upsets, bubonic plague, and smallpox.

Saffron crocus cultivation has long centred on a broad belt of Eurasia bounded by the Mediterranean Sea in the southwest to India and China in the northeast. The major producers of antiquity—Iran, Spain, India, and Greece—continue to dominate the world trade. […] Iran has accounted for around 90–93 percent of recent annual world production and thereby dominates the export market on a by-quantity basis. […]

The high cost of saffron is due to the difficulty of manually extracting large numbers of minute stigmas, which are the only part of the crocus with the desired aroma and flavour. An exorbitant number of flowers need to be processed in order to yield marketable amounts of saffron. Obtaining 1 lb (0.45 kg) of dry saffron requires the harvesting of some 50,000 flowers, the equivalent of an association football pitch’s area of cultivation, or roughly 7,140 m2 (0.714 ha).[14] By another estimate some 75,000 flowers are needed to produce one pound of dry saffron. […] Another complication arises in the flowers’ simultaneous and transient blooming. […] Bulk quantities of lower-grade saffron can reach upwards of US$500 per pound; retail costs for small amounts may exceed ten times that rate. In Western countries the average retail price is approximately US$1,000 per pound.[5] Prices vary widely elsewhere, but on average tend to be lower. The high price is somewhat offset by the small quantities needed in kitchens: a few grams at most in medicinal use and a few strands, at most, in culinary applications; there are between 70,000 and 200,000 strands in a pound.”

ii. Scramble for Africa.

“The “Scramble for Africa” (also the Partition of Africa and the Conquest of Africa) was the invasion and occupation, colonization and annexation of African territory by European powers during the period of New Imperialism, between 1881 and 1914. In 1870, 10 percent of Africa was under European control; by 1914 it was 90 percent of the continent, with only Abyssinia (Ethiopia) and Liberia still independent.”

Here’s a really neat illustration from the article:

Scramble-for-Africa-1880-1913

“Germany became the third largest colonial power in Africa. Nearly all of its overall empire of 2.6 million square kilometres and 14 million colonial subjects in 1914 was found in its African possessions of Southwest Africa, Togoland, the Cameroons, and Tanganyika. Following the 1904 Entente cordiale between France and the British Empire, Germany tried to isolate France in 1905 with the First Moroccan Crisis. This led to the 1905 Algeciras Conference, in which France’s influence on Morocco was compensated by the exchange of other territories, and then to the Agadir Crisis in 1911. Along with the 1898 Fashoda Incident between France and Britain, this succession of international crises reveals the bitterness of the struggle between the various imperialist nations, which ultimately led to World War I. […]

David Livingstone‘s explorations, carried on by Henry Morton Stanley, excited imaginations. But at first, Stanley’s grandiose ideas for colonisation found little support owing to the problems and scale of action required, except from Léopold II of Belgium, who in 1876 had organised the International African Association (the Congo Society). From 1869 to 1874, Stanley was secretly sent by Léopold II to the Congo region, where he made treaties with several African chiefs along the Congo River and by 1882 had sufficient territory to form the basis of the Congo Free State. Léopold II personally owned the colony from 1885 and used it as a source of ivory and rubber.

While Stanley was exploring Congo on behalf of Léopold II of Belgium, the Franco-Italian marine officer Pierre de Brazza travelled into the western Congo basin and raised the French flag over the newly founded Brazzaville in 1881, thus occupying today’s Republic of the Congo. Portugal, which also claimed the area due to old treaties with the native Kongo Empire, made a treaty with Britain on 26 February 1884 to block off the Congo Society’s access to the Atlantic.

By 1890 the Congo Free State had consolidated its control of its territory between Leopoldville and Stanleyville, and was looking to push south down the Lualaba River from Stanleyville. At the same time, the British South Africa Company of Cecil Rhodes was expanding north from the Limpopo River, sending the Pioneer Column (guided by Frederick Selous) through Matabeleland, and starting a colony in Mashonaland.

To the West, in the land where their expansions would meet, was Katanga, site of the Yeke Kingdom of Msiri. Msiri was the most militarily powerful ruler in the area, and traded large quantities of copper, ivory and slaves — and rumours of gold reached European ears. The scramble for Katanga was a prime example of the period. Rhodes and the BSAC sent two expeditions to Msiri in 1890 led by Alfred Sharpe, who was rebuffed, and Joseph Thomson, who failed to reach Katanga. Leopold sent four CFS expeditions. First, the Le Marinel Expedition could only extract a vaguely worded letter. The Delcommune Expedition was rebuffed. The well-armed Stairs Expedition was given orders to take Katanga with or without Msiri’s consent. Msiri refused, was shot, and the expedition cut off his head and stuck it on a pole as a “barbaric lesson” to the people. The Bia Expedition finished the job of establishing an administration of sorts and a “police presence” in Katanga.

Thus, the half million square kilometres of Katanga came into Leopold’s possession and brought his African realm up to 2,300,000 square kilometres (890,000 sq mi), about 75 times larger than Belgium. The Congo Free State imposed such a terror regime on the colonised people, including mass killings and forced labour, that Belgium, under pressure from the Congo Reform Association, ended Leopold II’s rule and annexed it in 1908 as a colony of Belgium, known as the Belgian Congo. […]

“Britain’s administration of Egypt and the Cape Colony contributed to a preoccupation over securing the source of the Nile River. Egypt was overrun by British forces in 1882 (although not formally declared a protectorate until 1914, and never an actual colony); Sudan, Nigeria, Kenya and Uganda were subjugated in the 1890s and early 20th century; and in the south, the Cape Colony (first acquired in 1795) provided a base for the subjugation of neighbouring African states and the Dutch Afrikaner settlers who had left the Cape to avoid the British and then founded their own republics. In 1877, Theophilus Shepstone annexed the South African Republic (or Transvaal – independent from 1857 to 1877) for the British Empire. In 1879, after the Anglo-Zulu War, Britain consolidated its control of most of the territories of South Africa. The Boers protested, and in December 1880 they revolted, leading to the First Boer War (1880–81). British Prime Minister William Gladstone signed a peace treaty on 23 March 1881, giving self-government to the Boers in the Transvaal. […] The Second Boer War, fought between 1899 and 1902, was about control of the gold and diamond industries; the independent Boer republics of the Orange Free State and the South African Republic (or Transvaal) were this time defeated and absorbed into the British Empire.”

There are a lot of unsourced claims in the article and some parts of it actually aren’t very good, but this is a topic about which I did not know much (I had no idea most of colonial Africa was acquired by the European powers as late as was actually the case). This is another good map from the article to have a look at if you just want the big picture.

iii. Cursed soldiers.

“The cursed soldiers (that is, “accursed soldiers” or “damned soldiers”; Polish: Żołnierze wyklęci) is a name applied to a variety of Polish resistance movements formed in the later stages of World War II and afterwards. Created by some members of the Polish Secret State, these clandestine organizations continued their armed struggle against the Stalinist government of Poland well into the 1950s. The guerrilla warfare included an array of military attacks launched against the new communist prisons as well as MBP state security offices, detention facilities for political prisoners, and concentration camps set up across the country. Most of the Polish anti-communist groups ceased to exist in the late 1940s or 1950s, hunted down by MBP security services and NKVD assassination squads.[1] However, the last known ‘cursed soldier’, Józef Franczak, was killed in an ambush as late as 1963, almost 20 years after the Soviet take-over of Poland.[2][3] […] Similar eastern European anti-communists fought on in other countries. […]

Armia Krajowa (or simply AK)-the main Polish resistance movement in World War II-had officially disbanded on 19 January 1945 to prevent a slide into armed conflict with the Red Army, including an increasing threat of civil war over Poland’s sovereignty. However, many units decided to continue on with their struggle under new circumstances, seeing the Soviet forces as new occupiers. Meanwhile, Soviet partisans in Poland had already been ordered by Moscow on June 22, 1943 to engage Polish Leśni partisans in combat.[6] They commonly fought Poles more often than they did the Germans.[4] The main forces of the Red Army (Northern Group of Forces) and the NKVD had begun conducting operations against AK partisans already during and directly after the Polish Operation Tempest, designed by the Poles as a preventive action to assure Polish rather than Soviet control of the cities after the German withdrawal.[5] Soviet premier Joseph Stalin aimed to ensure that an independent Poland would never reemerge in the postwar period.[7] […]

The first Polish communist government, the Polish Committee of National Liberation, was formed in July 1944, but declined jurisdiction over AK soldiers. Consequently, for more than a year, it was Soviet agencies like the NKVD that dealt with the AK. By the end of the war, approximately 60,000 soldiers of the AK had been arrested, and 50,000 of them were deported to the Soviet Union’s gulags and prisons. Most of those soldiers had been captured by the Soviets during or in the aftermath of Operation Tempest, when many AK units tried to cooperate with the Soviets in a nationwide uprising against the Germans. Other veterans were arrested when they decided to approach the government after being promised amnesty. In 1947, an amnesty was passed for most of the partisans; the Communist authorities expected around 12,000 people to give up their arms, but the actual number of people to come out of the forests eventually reached 53,000. Many of them were arrested despite promises of freedom; after repeated broken promises during the first few years of communist control, AK soldiers stopped trusting the government.[5] […]

The persecution of the AK members was only a part of the reign of Stalinist terror in postwar Poland. In the period of 1944–56, approximately 300,000 Polish people had been arrested,[21] or up to two million, by different accounts.[5] There were 6,000 death sentences issued, the majority of them carried out.[21] Possibly, over 20,000 people died in communist prisons including those executed “in the majesty of the law” such as Witold Pilecki, a hero of Auschwitz.[5] A further six million Polish citizens (i.e., one out of every three adult Poles) were classified as suspected members of a ‘reactionary or criminal element’ and subjected to investigation by state agencies.”

iv. Affective neuroscience.

Affective neuroscience is the study of the neural mechanisms of emotion. This interdisciplinary field combines neuroscience with the psychological study of personality, emotion, and mood.[1]

This article is actually related to the Delusion and self-deception book, which covered some of the stuff included in this article, but I decided I might as well include the link in this post. I think some parts of the article are written in a somewhat different manner than most wiki articles – there are specific paragraphs briefly covering the results of specific meta-analyses conducted in this field. I can’t really tell from this article if I actually like this way of writing a wiki article or not.

v. Hamming distance. Not a long article, but this is a useful concept to be familiar with:

“In information theory, the Hamming distance between two strings of equal length is the number of positions at which the corresponding symbols are different. In another way, it measures the minimum number of substitutions required to change one string into the other, or the minimum number of errors that could have transformed one string into the other. […]

The Hamming distance is named after Richard Hamming, who introduced it in his fundamental paper on Hamming codes Error detecting and error correcting codes in 1950.[1] It is used in telecommunication to count the number of flipped bits in a fixed-length binary word as an estimate of error, and therefore is sometimes called the signal distance. Hamming weight analysis of bits is used in several disciplines including information theory, coding theory, and cryptography. However, for comparing strings of different lengths, or strings where not just substitutions but also insertions or deletions have to be expected, a more sophisticated metric like the Levenshtein distance is more appropriate.”

vi. Menstrual synchrony. I came across that one recently in a book, and when I did it was obvious that the author had not read this article, and lacked some knowledge included in this article (the phenomenon was assumed to be real in the coverage, and theory was developed assuming it was real which would not make sense if it was not). I figured if that person didn’t know this stuff, a lot of other people – including people reading along here – probably also do not, so I should cover this topic somewhere. This is an obvious place to do so. Okay, on to the article coverage:

Menstrual synchrony, also called the McClintock effect,[2] is the alleged process whereby women who begin living together in close proximity experience their menstrual cycle onsets (i.e., the onset of menstruation or menses) becoming closer together in time than previously. “For example, the distribution of onsets of seven female lifeguards was scattered at the beginning of the summer, but after 3 months spent together, the onset of all seven cycles fell within a 4-day period.”[3]

Martha McClintock’s 1971 paper, published in Nature, says that menstrual cycle synchronization happens when the menstrual cycle onsets of two women or more women become closer together in time than they were several months earlier.[3] Several mechanisms have been hypothesized to cause synchronization.[4]

After the initial studies, several papers were published reporting methodological flaws in studies reporting menstrual synchrony including McClintock’s study. In addition, other studies were published that failed to find synchrony. The proposed mechanisms have also received scientific criticism. A 2013 review of menstrual synchrony concluded that menstrual synchrony is doubtful.[4] […] in a recent systematic review of menstrual synchrony, Harris and Vitzthum concluded that “In light of the lack of empirical evidence for MS [menstrual synchrony] sensu stricto, it seems there should be more widespread doubt than acceptance of this hypothesis.” […]

The experience of synchrony may be the result of the mathematical fact that menstrual cycles of different frequencies repeatedly converge and diverge over time and not due to a process of synchronization.[12] It may also be due to the high probability of menstruation overlap that occurs by chance.[6]

 

December 4, 2014 Posted by | Biology, Botany, Computer science, Geography, History, Medicine, Neurology, Psychology, Wikipedia | Leave a comment

100 Cases in Clinical Pathology

This book is another publication from the 100 Cases … series which I’ve talked about before – I refer to these posts for some general comments about what this series is like and some talk about the other books in the series which I’ve read. The book is much like the others, though of course the specific topics covered are different in the various publications. I liked this book and gave it 3 stars on goodreads. The book has three sections: a section dealing with ‘chemical pathology, immunology and genetics’; a section dealing with ‘histopathology’; and a section dealing with ‘haematology’. As usual I knew a lot more about some of the topics covered than I did about some of the others. Some cases were quite easy, others were not. Some of the stuff covered in Greenstein & Wood’s endocrinology text came in handy along the way and enabled me for example to easily identify a case of Cushing’s syndrome and a case of Graves’ disease. I don’t think I’ll spoil anything by noting that two of the cases in this book involved these disorders, but if you plan on reading it later on you may want to skip the coverage below, as I have included some general comments from the answer sections of the book in this post.

As someone who’s not working in the medical field and who will almost certainly never need to know how to interpret a water deprivation test (also covered in detail in Greenstein and Wood, incidentally), there are some parts of books like this one which are not particularly ‘relevant’ to me; however I’d argue that far from all the stuff included in a book like this one is ‘stuff you don’t need to know’, as there are also for example a lot of neat observations included about how specific symptoms (and symptom complexes) are linked to specific disorders, some related ideas about which other medical conditions might cause similar health problems, and which risk factors are potentially important to have in mind in specific contexts. If you’ve had occasional fevers, night sweats and experienced weight loss over the last few months, you should probably have seen a doctor a while ago – knowledge included in books like this one may make the reader perhaps a bit less likely to overlook an important and potentially treatable health problem, and/or increase awareness of potential modifiable risk factors in specific contexts. A problem is however that the book will be hard to read if you have not read any medical textbooks before, and in that case I would probably advise you against reading it as it’s almost certainly not worth the effort.

I have added a few observations from the book below.

“After a bone marrow transplant (and any associated chemotherapy), the main risks are infection (from low white cell counts and the use of immunosuppressants, such as cyclosporin), bleeding (from low platelet counts) and graft versus host disease (GVHD). […] An erythematous rash that develops on the palms or soles of the feet of a patient 10–30 days after a bone marrow transplant is characteristic of GVHD. […] GVHD is a potentially life-threatening problem that can occur in up to 80% of successful allogeneic bone marrow transplants. […] Clinically, GVHD manifests like an autoimmune disease with a macular-papular rash, jaundice and hepatosplenomegaly and ultimately organ fibrosis. It classically involves the skin, gastrointestinal tract and the liver. […] Depending on severity, treatment of acute GVHD may involve topical and intravenous steroid therapy, immunosuppression (e.g. cyclosporine), or biologic therapies targeting TNF-α […], a key inflammatory cytokine. […] Prognosis is related to response to treatment. The mortality of patients who completely respond can still be around 20%, and the mortality in those who do not respond is as high as 75%.”

“The leading indication for a liver transplant is alcoholic cirrhosis in adults and biliary atresia in children. […] The overall one-year survival of a liver transplant is over 90%, with 10-year survival of around 70%. […] Transplant rejection can be classified by time course, which relates to the underlying immune mechanism: • Hyperacute organ rejection occurs within minutes of the graft perfusion in the operating theatre. […] The treatment for hyperacute rejection is immediate removal of the graft. • Acute organ rejection take place a number of weeks after the transplant […] The treatment for acute rejection includes high dose steroids. • Chronic organ rejection can take place months to years after the transplant. […] As it is irreversible, treatment for chronic rejection is difficult, and may include re-transplantation.”

“Chronic kidney disease (CKD) is characterized by a reduction in GFR over a period of 3 or more months (normal GFR is >90–120 mL/min). It arises from a progressive impairment of renal function with a decrease in the number of functioning nephrons; generally, patients remain asymptomatic until GFR reduces to below 15 mL/min (stage V CKD). Common causes of CKD are (1) diabetes mellitus, (2) hypertension, (3) glomerulonephritis, (4) renovascular disease, (5) chronic obstruction or interstitial nephritis, and (6) hereditary or cystic renal disease”

“The definition of an aneurysm is an abnormal permanent focal dilatation of all the layers of a blood vessel. An AAA [abdominal aortic aneurysm] is defined when the aortic diameter, as measured below the level of the renal arteries, is one and a half times normal. Women have smaller aortas, but for convenience, more than 3 cm qualifies as aneurysmal. The main risk factors for aneurysm formation are male gender, smoking, hypertension, Caucasian/European descent and atherosclerosis. Although atherosclerosis is a risk factor and both diseases share common predisposing factors, there are also differences. Atherosclerosis is primarily a disease of the intima, the innermost layer of the vessel wall, whereas in aneurysms there is degeneration of the media, the middle layer. […] The annual risk of rupture equals and begins to outstrip the risk of dying from surgery when the aneurysm exceeds 5.5 cm. This is the size above which surgical repair is recommended, comorbidities permitting. […] Catastrophic rupture, as in this case, presents with hypovolaemic shock and carries a dismal prognosis.” [The patient in the case history died soon after having arrived at the hospital]

“Stroke refers to an acquired focal neurological deficit caused by an acute vascular event. The neurological deficit persists beyond 24 hours, in contrast to a transient ischaemic attack (TIA) where symptoms resolve within 24 hours, although the distinction is now blurred with the advent of thrombolysis. […] Strokes are broadly categorized into ischaemic and haemorrhagic types, the majority being ischaemic. The pathophysiology in a haemorrhagic stroke is rupture of a blood vessel causing extravasation of blood into the brain substance with tissue damage and disruption of neuronal connections. The resulting haematoma also compresses surrounding normal tissue. In most ischaemic strokes, there is thromboembolic occlusion of vessels due to underlying atherosclerosis of the aortic arch and carotid arteries. In 15–20% of cases, there is atherosclerotic disease of smaller intrinsic blood vessels within the brain[…]. A further 15–20% are due to emboli from the heart. […] The territory and the extent of the infarct influences the prognosis; [for example] expressive dysphasia and right hemiparesis are attributable to infarcts in Broca’s area and the motor cortex, both frontal lobe territories supplied by the left middle cerebral artery.”

“The stereotypical profile of a gallstone patient is summed up by the 4Fs: female, fat, fertile and forty. However, while gallstones are twice as common in females, increasing age is a more important risk factor. Above the age of 60, 10–20% of the Western population have gallstones. […] Most people with cholelithiasis are asymptomatic, but there is a 1–4% annual risk of developing symptoms or complications. […] Complications depend on the size of the stones. Smaller stones may escape into the common bile duct, but may lodge at the narrowing of the hepatopancreatic sphincter (sphincter of Oddi), obstructing the common bile duct and pancreatic duct, leading to obstructive jaundice and pancreatitis respectively. […] In most series, alcohol and gallstones each account for 30–35% of cases [of acute pancreatitis]. […] Once symptomatic, the definitive treatment of gallstone disease is generally surgical via a cholecystectomy.”

“Breast cancer affects 1 in 8 women (lifetime risk) in the UK. […] Between 10 and 40% of women who are found to have a mass by mammography will have breast cancer. […] The presence of lymphovascular invasion indicates the likelihood of spread of tumour cells beyond the breast, thereby conferring a poorer outlook. Without lymph node involvement, the 10-year disease-free survival is close to 70–80% but falls progressively with the number of involved nodes.”

“Melanoma is a cancer of melanocytes, the pigmented cells in the skin, and is caused by injury to lightly pigmented skin by excessive exposure to ultraviolet (UV) radiation […] The change in colour of a pre-existing pigmented lesion with itching and bleeding and irregular margins on examination are indicators of transformation to melanoma. Melanomas progress through a radial growth phase to a vertical growth phase. In the radial growth phase, the lesion expands horizontally within the epidermis and superficial dermis often for a long period of time. Progression to the vertical phase is characterized by downward growth of the lesion into the deeper dermis and with absence of maturation of cells at the advancing front. During this phase, the lesion acquires the potential to metastasize through lymphovascular channels. The probability of this happening increases with increasing depth of invasion (Breslow thickness) by the melanoma cells. […] The ABCDE mnemonic aids in the diagnosis of melanoma: Asymmetry – melanomas are likely to be irregular or asymmetrical. Border – melanomas are more likely to have an irregular border with jagged edges. Colour – melanomas tend to be variegated in colour […]. Diameter – melanomas are usually more than 7 mm in diameter. Evolution – look for changes in the size, shape or colour of a mole.”

“CLL [chronic lymphocytic leukaemia] is the most common leukaemia in the Western world. Typically, it is picked up via an incidental lymphocytosis in an asymptomatic individual. […] The disease is staged according to the Binet classification. Typically, patients with Binet stage A disease require no immediate treatment. Symptomatic stage B and all stage C patients receive chemotherapy. […] cure is rare and the aim is to achieve periods of remission and symptom control. […] The median survival in CLL is between four and six years, though some patients survive a decade or more. […] There is […] a tendency of CLL to transform into a more aggressive leukaemia, typically a prolymphocytic transformation (in 15–30% of patients) or, less commonly (<10% of cases), transformation into a diffuse large B-cell lymphoma (a so-called Richter transformation). Appearance of transformative disease is an ominous sign, with few patients surviving for more than a year with such disease.”

“Pain, swelling, warmth, tenderness and immobility are the five cardinal signs of acute inflammation.”

“Osteomyelitis is an infection of bone that is characterized by progressive inflammatory destruction with the formation of sequestra (dead pieces of bone within living bone), which if not treated leads to new bone formation occurring on top of the dead and infected bone. It can affect any bone, although it occurs most commonly in long bones. […] Bone phagocytes engulf the bacteria and release osteolytic enzymes and toxic oxygen free radicals, which lyse the surrounding bone. Pus raises intraosseus pressure and impairs blood flow, resulting in thrombosis of the blood vessels. Ischaemia results in bone necrosis and devitalized segments of bone (known as sequestra). These sequestra are important in the pathogenesis of non-resolving infection, acting as an ongoing focus of infection if not removed. Osteomyelitis is one of the most difficult infections to treat. Treatment may require surgery in addition to antibiotics, especially in chronic osteomyelitis where sequestra are present. […] Poorly controlled diabetics are at increased risk of infections, and having an infection leads to poor control of diabetes via altered physiology occurring during infection. Diabetics are prone to developing foot ulcers, which in turn are prone to becoming infected, which then act as a source of bacteria for infecting the contiguous bones of the feet. This process is exacerbated in patients with peripheral neuropathy, poor diabetic control and peripheral vascular disease, as these all increase the risk of development of skin breakdown and subsequent osteomyelitis.” [The patient was of course a diabetic…]

“Recent onset fever and back pain suggest an upper UTI [urinary tract infection]. UTIs are classified by anatomy into lower and upper UTIs. Lower UTIs refer to infections at or below the level of the bladder, and include cystitis, urethritis, prostatitis, and epididymitis (the latter three being more often sexually transmitted). Upper UTIs refer to infection above the bladder, and include the ureters and kidneys. Infection of the urinary tract above the bladder is known as pyelonephritis [which] may be life threatening or lead to permanent kidney damage if not promptly treated. UTIs are also classified as complicated or uncomplicated. UTIs in men, the elderly, pregnant women, those who have an indwelling catheter, and anatomic or functional abnormality of the urinary tract are considered to be complicated. A complicated UTI will often receive longer courses of broader spectrum antibiotics. Importantly, the clinical history alone of dysuria and frequency (without vaginal discharge) is associated with more than 90% probability of a UTI in healthy women. […] In women, a UTI develops when urinary pathogens from the bowel or vagina colonize the urethral mucosa, and ascend via the urethra into the bladder. During an uncomplicated symptomatic UTI in women, it is rare for infection to ascend via the ureter into the kidney to cause pyelonephritis. […] Up to 40% of uncomplicated lower UTIs in women will resolve spontaneously without antimicrobial therapy. The use of antibiotics in this cohort is controversial when taking into account the side effects of antibiotics and their effect on normal flora. If prescribed, antibiotics for uncomplicated lower UTIs should be narrow-spectrum […] Most healthcare-associated UTIs are associated with the use of urinary catheters. Each day the catheter remains in situ, the risk of UTI rises by around 5%. Thus inserting catheters only when absolutely needed, and ensuring they are removed as soon as possible, can prevent these.”

September 24, 2014 Posted by | alcohol, Books, Cancer/oncology, Cardiology, Diabetes, Immunology, Medicine, Microbiology, Nephrology, Neurology | Leave a comment