Econstudentlog

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, medicine | Leave a comment

Anesthesia

“A recent study estimated that 234 million surgical procedures requiring anaesthesia are performed worldwide annually. Anaesthesia is the largest hospital specialty in the UK, with over 12,000 practising anaesthetists […] In this book, I give a short account of the historical background of anaesthetic practice, a review of anaesthetic equipment, techniques, and medications, and a discussion of how they work. The risks and side effects of anaesthetics will be covered, and some of the subspecialties of anaesthetic practice will be explored.”

I liked the book, and I gave it three stars on goodreads; I was closer to four stars than two. Below I have added a few sample observations from the book, as well as what turned out in the end to be actually a quite considerable number of links (more than 60 it turned out, from a brief count) to topics/people/etc. discussed or mentioned in the text. I decided to spend a bit more time finding relevant links than I’ve previously done when writing link-heavy posts, so in this post I have not limited myself to wikipedia articles and I e.g. also link directly to primary literature discussed in the coverage. The links provided are, as usual, meant to be indicators of which kind of stuff is covered in the book, rather than an alternative to the book; some of the wikipedia articles in particular I assume are not very good (the main point of a link to a wikipedia article of questionable quality should probably be taken to be an indication that I consider ‘awareness of the existence of concept X’ to be of interest/important also to people who have not read this book, even if no great resource on the topic was immediately at hand to me).

Sample observations from the book:

“[G]eneral anaesthesia is not sleep. In physiological terms, the two states are very dissimilar. The term general anaesthesia refers to the state of unconsciousness which is deliberately produced by the action of drugs on the patient. Local anaesthesia (and its related terms) refers to the numbness produced in a part of the body by deliberate interruption of nerve function; this is typically achieved without affecting consciousness. […] The purpose of inhaling ether vapour [in the past] was so that surgery would be painless, not so that unconsciousness would necessarily be produced. However, unconsciousness and immobility soon came to be considered desirable attributes […] For almost a century, lying still was the only reliable sign of adequate anaesthesia.”

“The experience of pain triggers powerful emotional consequences, including fear, anger, and anxiety. A reasonable word for the emotional response to pain is ‘suffering’. Pain also triggers the formation of memories which remind us to avoid potentially painful experiences in the future. The intensity of pain perception and suffering also depends on the mental state of the subject at the time, and the relationship between pain, memory, and emotion is subtle and complex. […] The effects of adrenaline are responsible for the appearance of someone in pain: pale, sweating, trembling, with a rapid heart rate and breathing. Additionally, a hormonal storm is activated, readying the body to respond to damage and fight infection. This is known as the stress response. […] Those responses may be abolished by an analgesic such as morphine, which will counteract all those changes. For this reason, it is routine to use analgesic drugs in addition to anaesthetic ones. […] Typical anaesthetic agents are poor at suppressing the stress response, but analgesics like morphine are very effective. […] The hormonal stress response can be shown to be harmful, especially to those who are already ill. For example, the increase in blood coagulability which evolved to reduce blood loss as a result of injury makes the patient more likely to suffer a deep venous thrombosis in the leg veins.”

“If we monitor the EEG of someone under general anaesthesia, certain identifiable changes to the signal occur. In general, the frequency spectrum of the signal slows. […] Next, the overall power of the signal diminishes. In very deep general anaesthesia, short periods of electrical silence, known as burst suppression, can be observed. Finally, the overall randomness of the signal, its entropy, decreases. In short, the EEG of someone who is anaesthetized looks completely different from someone who is awake. […] Depth of anaesthesia is no longer considered to be a linear concept […] since it is clear that anaesthesia is not a single process. It is now believed that the two most important components of anaesthesia are unconsciousness and suppression of the stress response. These can be represented on a three-dimensional diagram called a response surface. [Here’s incidentally a recent review paper on related topics, US]”

“Before the widespread advent of anaesthesia, there were very few painkilling options available. […] Alcohol was commonly given as a means of enhancing the patient’s courage prior to surgery, but alcohol has almost no effect on pain perception. […] For many centuries, opium was the only effective pain-relieving substance known. […] For general anaesthesia to be discovered, certain prerequisites were required. On the one hand, the idea that surgery without pain was achievable had to be accepted as possible. Despite tantalizing clues from history, this idea took a long time to catch on. The few workers who pursued this idea were often openly ridiculed. On the other, an agent had to be discovered that was potent enough to render a patient suitably unconscious to tolerate surgery, but not so potent that overdose (hence accidental death) was too likely. This agent also needed to be easy to produce, tolerable for the patient, and easy enough for untrained people to administer. The herbal candidates (opium, mandrake) were too unreliable or dangerous. The next reasonable candidate, and every agent since, was provided by the proliferating science of chemistry.”

“Inducing anaesthesia by intravenous injection is substantially quicker than the inhalational method. Inhalational induction may take several minutes, while intravenous induction happens in the time it takes for the blood to travel from the needle to the brain (30 to 60 seconds). The main benefit of this is not convenience or comfort but patient safety. […] It was soon discovered that the ideal balance is to induce anaesthesia intravenously, but switch to an inhalational agent […] to keep the patient anaesthetized during the operation. The template of an intravenous induction followed by maintenance with an inhalational agent is still widely used today. […] Most of the drawbacks of volatile agents disappear when the patient is already anaesthetized [and] volatile agents have several advantages for maintenance. First, they are predictable in their effects. Second, they can be conveniently administered in known quantities. Third, the concentration delivered or exhaled by the patient can be easily and reliably measured. Finally, at steady state, the concentration of volatile agent in the patient’s expired air is a close reflection of its concentration in the patient’s brain. This gives the anaesthetist a reliable way of ensuring that enough anaesthetic is present to ensure the patient remains anaesthetized.”

“All current volatile agents are colourless liquids that evaporate into a vapour which produces general anaesthesia when inhaled. All are chemically stable, which means they are non-flammable, and not likely to break down or be metabolized to poisonous products. What distinguishes them from each other are their specific properties: potency, speed of onset, and smell. Potency of an inhalational agent is expressed as MAC, the minimum alveolar concentration required to keep 50% of adults unmoving in response to a standard surgical skin incision. MAC as a concept was introduced […] in 1963, and has proven to be a very useful way of comparing potencies of different anaesthetic agents. […] MAC correlates with observed depth of anaesthesia. It has been known for over a century that potency correlates very highly with lipid solubility; that is, the more soluble an agent is in lipid […], the more potent an anaesthetic it is. This is known as the Meyer-Overton correlation […] Speed of onset is inversely proportional to water solubility. The less soluble in water, the more rapidly an agent will take effect. […] Where immobility is produced at around 1.0 MAC, amnesia is produced at a much lower dose, typically 0.25 MAC, and unconsciousness at around 0.5 MAC. Therefore, a patient may move in response to a surgical stimulus without either being conscious of the stimulus, or remembering it afterwards.”

“The most useful way to estimate the body’s physiological reserve is to assess the patient’s tolerance for exercise. Exercise is a good model of the surgical stress response. The greater the patient’s tolerance for exercise, the better the perioperative outcome is likely to be […] For a smoker who is unable to quit, stopping for even a couple of days before the operation improves outcome. […] Dying ‘on the table’ during surgery is very unusual. Patients who die following surgery usually do so during convalescence, their weakened state making them susceptible to complications such as wound breakdown, chest infections, deep venous thrombosis, and pressure sores.”

Mechanical ventilation is based on the principle of intermittent positive pressure ventilation (IPPV), gas being ‘blown’ into the patient’s lungs from the machine. […] Inflating a patient’s lungs is a delicate process. Healthy lung tissue is fragile, and can easily be damaged by overdistension (barotrauma). While healthy lung tissue is light and spongy, and easily inflated, diseased lung tissue may be heavy and waterlogged and difficult to inflate, and therefore may collapse, allowing blood to pass through it without exchanging any gases (this is known as shunt). Simply applying higher pressures may not be the answer: this may just overdistend adjacent areas of healthier lung. The ventilator must therefore provide a series of breaths whose volume and pressure are very closely controlled. Every aspect of a mechanical breath may now be adjusted by the anaesthetist: the volume, the pressure, the frequency, and the ratio of inspiratory time to expiratory time are only the basic factors.”

“All anaesthetic drugs are poisons. Remember that in achieving a state of anaesthesia you intend to poison someone, but not kill them – so give as little as possible. [Introductory quote to a chapter, from an Anaesthetics textbook – US] […] Other cells besides neurons use action potentials as the basis of cellular signalling. For example, the synchronized contraction of heart muscle is performed using action potentials, and action potentials are transmitted from nerves to skeletal muscle at the neuromuscular junction to initiate movement. Local anaesthetic drugs are therefore toxic to the heart and brain. In the heart, local anaesthetic drugs interfere with normal contraction, eventually stopping the heart. In the brain, toxicity causes seizures and coma. To avoid toxicity, the total dose is carefully limited”.

Links of interest:

Anaesthesia.
General anaesthesia.
Muscle relaxant.
Nociception.
Arthur Ernest Guedel.
Guedel’s classification.
Beta rhythm.
Frances Burney.
Laudanum.
Dwale.
Henry Hill Hickman.
Horace Wells.
William Thomas Green Morton.
Diethyl ether.
Chloroform.
James Young Simpson.
Joseph Thomas Clover.
Barbiturates.
Inhalational anaesthetic.
Antisialagogue.
Pulmonary aspiration.
Principles of Total Intravenous Anaesthesia (TIVA).
Propofol.
Patient-controlled analgesia.
Airway management.
Oropharyngeal airway.
Tracheal intubation.
Laryngoscopy.
Laryngeal mask airway.
Anaesthetic machine.
Soda lime.
Sodium thiopental.
Etomidate.
Ketamine.
Neuromuscular-blocking drug.
Neostigmine.
Sugammadex.
Gate control theory of pain.
Multimodal analgesia.
Hartmann’s solution (…what this is called seems to be depending on whom you ask, but it’s called Hartmann’s solution in the book…).
Local anesthetic.
Karl Koller.
Amylocaine.
Procaine.
Lidocaine.
Regional anesthesia.
Spinal anaesthesia.
Epidural nerve block.
Intensive care medicine.
Bjørn Aage Ibsen.
Chronic pain.
Pain wind-up.
John Bonica.
Twilight sleep.
Veterinary anesthesia.
Pearse et al. (results of paper briefly discussed in the book).
Awareness under anaesthesia (skip the first page).
Pollard et al. (2007).
Postoperative nausea and vomiting.
Postoperative cognitive dysfunction.
Monk et al. (2008).
Malignant hyperthermia.
Suxamethonium apnoea.

February 13, 2017 Posted by | books, Chemistry, medicine, papers, Pharmacology | 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, diabetes, medicine, Neurology | 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, diabetes, 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, medicine, Neurology, personal | Leave a comment

Integrated Diabetes Care (II)

Here’s my first post about the book. In this post I’ll provide some coverage of the last half of the text.

Some stuff from the chapters dealing with the UK:

“we now know that reducing the HbA1c too far and fast in some patients can be harmful [7]. This is a particularly important issue, where primary care is paid through the Quality Outcomes Framework (QoF), a general practice “pay for performance” programme [8]. A major item within QoF, is the proportion of patients below HbA1c criteria: such reporting is not linked to rates of hypoglycaemia, ambulance call outs or hospitalisation, i.e., a practice could receive a high payment through achieving the QoF target, but with a high hospitalisation/ambulance callout rate.”

“nationwide audit data for England 2009–2010 showed that […] targets for HbA1c (≤7.5%/58.5 mmol/mol), blood pressure (BP) (<140/80 mmHg) and total cholesterol (<4.0 mmol/l) were achieved in only 67 %, 69% and 41 % of people with T2D.”

One thing that is perhaps worth noting here before moving any further is that the fact that you have actual data on this stuff is in itself indicative of an at least reasonable standard of care, compared to many places; in a lot of countries you just don’t have data on this kind of stuff, and it seems highly unlikely to me that the default assumption should be that things are going great in places where you do not have data on this kind of thing. Denmark also, incidentally, has a similar audit system, the results of which I’ve discussed in some detail before here on the blog).

“Our local audit data shows that approximately 85–90 % of patients with diabetes are managed by GPs and practice nurses in Coventry and Warwickshire. Only a small proportion of newly diagnosed patients with T2D (typically around 5–10 %) who attend the DESMOND (Diabetes Education and Self-Management for Ongoing and Newly Diagnosed) education programme come into contact with some aspect of the specialist services [12]. […] Payment by results (PBR) has […] actively, albeit indirectly, disincentivised primary care to seek opinion from specialist services [13]. […] Large volumes of data are collected by various services ranging between primary care, local laboratory facilities, ambulance services, hospital clinics (of varying specialties), retinal screening services and several allied healthcare professionals. However, the majority of these systems are not unified and therefore result in duplication of data collection and lack of data utilisation beyond the purpose of collection. This can result in missed opportunities, delayed communication, inability to use electronic solutions (prompts, alerts, algorithms etc.), inefficient use of resources and patient fatigue (repeated testing but no apparent benefit). Thus, in the majority of the regions in England, the delivery of diabetes care is disjointed and lacks integration. Each service collects and utilises data for their own “narrow” purpose, which could be used in a holistic way […] Potential consequences of the introduction of multiple service providers are fragmentation of care, reductions in continuity of care and propagation of a reluctance to refer on to a more specialist service [9]. […] There are calls for more integration and less fragmentation in health-care [30], yet so far, the major integration projects in England have revealed negligible, if any, benefits [25, 32]. […] to provide high quality care and reduce the cost burden of diabetes, any integrated diabetes care models must prioritise prevention and early aggressive intervention over downstream interventions (secondary and tertiary prevention).”

“It is estimated that 99 % of diabetes care is self-management […] people with diabetes spend approximately only 3 h a year with healthcare professionals (versus 8757 h of self-management)” [this is a funny way of looking at things, which I’d never really considered before.]

“In a traditional model of diabetes care the rigid divide between primary and specialist care is exacerbated by the provision of funding. For example the tariff system used in England, to pay for activity in specialist care, can create incentives for one part of the system to “hold on” to patients who might be better treated elsewhere. This system was originally introduced to incentivise providers to increase elective activity and reduce waiting times. Whilst it has been effective for improving access to planned care, it is not so well suited to achieving the continuity of care needed to facilitate integrated care [37].”

“Currently in the UK there is a miss-match between what the healthcare policies require and what the workforce is actually being trained for. […]  For true integrated care in diabetes and the other long term condition specialties to work, the education and training needs for both general practitioners and hospital specialists need to be more closely aligned.”

The chapter on Germany (Baden-Württemberg):

“An analysis of the Robert Koch-Institute (RKI) from 2012 shows that more than 50 % of German people over 65 years suffer from at least one chronic disease, approximately 50 % suffer from two to four chronic diseases, and over a quarter suffer from five or more diseases [3]. […] Currently the public sector covers the majority (77 %) of health expenditures in Germany […] An estimated number of 56.3 million people are living with diabetes in Europe [16]. […]  The mean age of the T2DM-cohort [from Kinzigtal, Germany] in 2013 was 71.2 years and 53.5 % were women. In 2013 the top 5 co-morbidities of patients with T2DM were essential hypertension (78.3 %), dyslipidaemia (50.5 %), disorders of refraction and accommodation (38.2 %), back pain (33.8 %) and obesity (33.3 %). […] T2DM in Kinzigtal was associated with mean expenditure of 5,935.70 € per person in 2013 (not necessarily only for diabetes care ) including 40 % from inpatient stays, 24 % from drug prescriptions, 19 % from physician remuneration in ambulatory care and the rest from remedies and adjuvants (e.g., insulin pen systems, wheelchairs, physiotherapy, etc.), work incapacity or rehabilitation.”

-ll- Netherlands:

“Zhang et al. [10] […] reported that globally, 12 % of health expenditures […] per person were spent on diabetes in 2010. The expenditure varies by region, age group, gender, and country’s income level.”

“Over the years many approaches [have been] introduced to improve the quality and continuity of care for chronic diseases. […] the Dutch minister of health approved, in 2007, the introduction of bundled-care (known is the Netherlands as a ‘chain-of-care’) approach for integrated chronic care, with special attention to diabetes. […] With a bundled payment approach – or episode-based payment – multiple providers are reimbursed a single sum of money for all services related to an episode of care (e.g., hospitalisation, including a period of post-acute care). This is in contrast to a reimbursement for each individual service (fee-for-service), and it is expected that this will reduce the volume of services provided and consequently lead to a reduction in spending. Since in a fee-for-service system the reimbursement is directly related to the volume of services provided, there is little incentive to reduce unnecessary care. The bundled payment approach promotes [in theory… – US] a more efficient use of services [26] […] As far as efficiency […] is concerned, after 3 years of evaluation, several changes in care processes have been observed, including task substitution from GPs to practice nurses and increased coordination of care [31, 36], thus improving process costs. However, Elissen et al. [31] concluded that the evidence relating to changes in process and outcome indicators, remains open to doubt, and only modest improvements were shown in most indicators. […] Overall, while the Dutch approach to integrated care, using a bundled payment system with a mixed payer approach, has created a limited improvement in integration, there is no evidence that the approach has reduced morbidity and premature mortality: and it has come at an increased cost.”

-ll- Sweden:

“In 2013 Sweden spent the equivalent of 4,904 USD per capita on health [OECD average: 3,453 USD], with 84 % of the expenditure coming from public sources [OECD average: 73 %]. […] Similarly high proportions [of public spending] can be found in the Netherlands (88 %), Norway (85 %) and Denmark (84 %) [11]. […] Sweden’s quality registers, for tracking the quality of care that patients receive and the corresponding outcomes for several conditions, are among the most developed across the OECD [17]. Yet, the coordination of care for patients with complex needs is less good. Only one in six patients had contact with a physician or specialist nurse after discharge from hospital for stroke, again with substantial variation across counties. Fewer than half of patients with type 1 diabetes […] have their blood pressure adequately controlled, with a considerable variation (from 26 % to 68 %) across counties [17]. […] at 260 admissions per 100,000 people aged over 80, avoidable hospital admissions for uncontrolled diabetes in Sweden’s elderly population are the sixth highest in the OECD, and about 1.5 times higher than in Denmark.”

“Waiting times [in Sweden] have long been a cause of dissatisfaction [19]. In an OECD ranking of 2011, Sweden was rated second worst [20]. […] Sweden introduced a health-care guarantee in 2005 [guaranteeing fast access in some specific contexts]. […] Most patients who appeal under the health-care guarantee and [are] prioritised in the “queue” ha[ve] acute conditions rather than medical problems as a consequence of an underlying chronic disease. Patients waiting for a hip replacement or a cataract surgery are cured after surgery and no life-long follow-up is needed. When such patients are prioritised, the long-term care for patients with chronic diseases is “crowded out,” lowering their priority and risking worse outcomes. The health-care guarantee can therefore lead to longer intervals between checkups, with difficulties in accessing health care if their pre-existing condition has deteriorated.”

“Within each region / county council the care of patients with diabetes is divided. Patients with type 1 diabetes get their care at specialist clinics in hospitals and the majority of patients with type 2 diabetes in primary care . Patients with type 2 diabetes who have severe complications are referred to the Diabetes Clinics at the hospital. Approximately 10 % of all patients with type 2 continue their care at the hospital clinics. They are almost always on insulin in high doses often in combination with oral agents but despite massive medication many of these patients have difficulties to achieve metabolic balance. Patients with advanced complications such as foot ulcers, macroangiopathic manifestations and treatment with dialysis are also treated at the hospitals.”

Do keep in mind here that even if only 10% of type 2 patients are treated in a hospital setting, type 2 patients may still make up perhaps half or more of the diabetes patients treated in a hospital setting; type 2 prevalence is much, much higher than type 1 prevalence. Also, in view of such treatment- and referral patterns the default assumption when doing comparative subgroup analyses should always be that the outcomes of type 2 patients treated in a hospital setting should be expected to be much worse than the outcomes of type 2 patients treated in general practice; they’re in much poorer health than the diabetics treated in general practice, or they wouldn’t be treated in a hospital setting in the first place. A related point is that regardless of how great the hospitals are at treating the type 2 patients (maybe in some contexts there isn’t actually much of a difference in outcomes between these patients and type 2 patients treated in general practice, even though you’d expect there to be one?), that option will usually not be scalable. Also, it’s to be expected that these patients are more expensive than the default type 2 patient treated by his GP [and they definitely are: “Only if severe complications arise [in the context of a type 2 patient] is the care shifted to specialised clinics in hospitals. […] these patients have the most expensive care due to costly treatment of for example foot ulcers and renal insufficiency”]; again, they’re sicker and need more comprehensive care. They would need it even if they did not get it in a hospital setting, and there are costs associated with under-treatment as well.

“About 90 % of the children [with diabetes in Sweden] are classified as having Type 1 diabetes based on positive autoantibodies and a few percent receive a diagnosis of “Maturity Onset Diabetes of the Young” (MODY) [39]. Type 2 diabetes among children is very rare in Sweden.”

Lastly, some observations from the final chapter:

“The paradox that we are dealing with is that in spite of health professionals wanting the best for their patients on a patient by patient basis, the way that individuals and institutions are organised and paid, directly influences the clinical decisions that are made. […] Naturally, optimising personal care and the provider/purchaser-commissioner budget may be aligned, but this is where diabetes poses substantial problems from a health system point of view: The majority of adverse diabetes outcomes […] are many years in the future, so a system based on this year’s budget will often not prioritise the future […] Even for these adverse “diabetes” outcomes, other clinical factors contribute to the end result. […]  attribution to diabetes may not be so obvious to those seeking ways to minimise expenditure.”

[I incidentally tried to get this point across in a recent discussion on SSC, but I’m not actually sure the point was understood, presumably because I did not explain it sufficiently clearly or go into enough detail. It is my general impression, on a related note, that many people who would like to cut down on the sort of implicit public subsidization of unhealthy behaviours that most developed economies to some extent engage in these days do not understand well enough the sort of problems that e.g. the various attribution problems and how to optimize ‘post-diagnosis care’ (even if what you want to optimize is the cost minimization function…) cause in specific contexts. As I hope my comments indicate in that thread, I don’t think these sorts of issues can be ignored or dealt with in some very simple manner – and I’m tempted to say that if you think they can, you don’t know enough about these topics. I say that as one of those people who would like people who engage in risky behaviours to pay a larger (health) risk premium than they currently do].

[Continued from above, …problems from a health system point of view:]
“Payment for ambulatory diabetes care , which is essentially the preventative part of diabetes care, usually sits in a different budget to the inpatient budget where the big expenses are. […] good evidence for reducing hospitalisation through diabetes integrated care is limited […] There is ample evidence [11, 12] where clinicians own, and profit from, other services (e.g., laboratory, radiology), that referral rates are increased, often inappropriately […] Under the English NHS, the converse exists, where GPs, either holding health budgets, or receiving payments for maintaining health budgets [13], reduce their referrals to more specialist care. While this may be appropriate in many cases, it may result in delays and avoidance of referrals, even when specialist care is likely to be of benefit. [this would be the under-treatment I was talking about above…] […] There is a mantra that fragmentation of care and reductions in continuity of care are likely to harm the quality of care [14], but hard evidence is difficult to obtain.”

“The problems outlined above, suggest that any health system that fails to take account of the need to integrate the payment system from both an immediate and long term perspective, must be at greater risk of their diabetes integration attempts failing and/or being unsustainable. […] There are clearly a number of common factors and several that differ between successful and less successful models. […] Success in these models is usually described in terms of hospitalisation (including, e.g., DKA, amputation, cardiovascular disease events, hypoglycaemia, eye disease, renal disease, all cause), metabolic outcomes (e.g., HbA1c ), health costs and access to complex care. Some have described patient related outcomes, quality of life and other staff satisfaction, but the methodology and biases have often not been open to scrutiny. There are some methodological issues that suggest that many of those with positive results may be illusory and reflect the pre-existing landscape and/or wider changes, particular to that locality. […] The reported “success” of intermediate diabetes clinics run by English General Practitioners with a Special Interest led to extension of the model to other areas. This was finally tested in a randomised controlled trial […] and shown to be a more costly model with no real benefit for patients or the system. Similarly in East Cambs and Fenland, the 1 year results suggested major reductions in hospitalisation and costs in practices participating fully in the integrated care initiative, compared with those who “engaged” later [9]. However, once the trends in neighbouring areas and among those without diabetes were accounted for, it became clear that the benefits originally reported were actually due to wider hospitalisation reductions, not just in those with diabetes. Studies of hospitalisation /hospital costs that do not compare with rates in the non-diabetic population need to be interpreted with caution.”

“Kaiser Permanente is often described as a great diabetes success story in the USA due to its higher than peer levels of, e.g., HbA1c testing [23]. However, in the 2015 HEDIS data, levels of testing, metabolic control achieved and complication rates show quality metrics lower than the English NHS, in spite of the problems with the latter [23]. Furthermore, HbA1c rates above 9 % remain at approximately 20 %, in Southern California [24] or 19 % in Northern California [25], a level much higher than that in the UK […] Similarly, the Super Six model […] has been lauded as a success, as a result of reductions in patients with, e.g., amputations. However, these complications were in the bottom quartile of performance for these outcomes in England [26] and hence improvement would be expected with the additional diabetes resources invested into the area. Amputation rates remain higher than the national average […] Studies showing improvement from a low baseline do not necessarily provide a best practice model, but perhaps a change from a system that required improvement. […] Several projects report improvements in HbA1c […] improvements in HbA1c, without reports of hypoglycaemia rates and weight gain, may be associated with worse outcomes as suggested from the ACCORD trial [28].”

December 18, 2016 Posted by | books, diabetes, economics, medicine | Leave a comment

The Ageing Immune System and Health (I)

as we age, we observe a greater heterogeneity of ability and health. The variation in, say, walking speed is far greater in a group of 70 year olds, than in a group on 20 year olds. This makes the study of ageing and the factors driving that heterogeneity of health and functional ability in old age vital. […] The study of the immune system across the lifespan has demonstrated that as we age the immune system undergoes a decline in function, termed immunosenescence. […] the decline in function is not universal across all aspects of the immune system, and neither is the magnitude of functional loss similar between individuals. The theory of inflammageing, which represents a chronic low grade inflammatory state in older people, has been described as a major consequence of immunosenescence, though lifestyle factors such as reduced physical activity and increased adiposity also play a major role […] In poor health, older people accumulate disease, described as multimorbidity. This in turn means traditional single system based health care becomes less valid as each system affected by disease impacts on other systems. This leads some older people to be at greater risk of adverse events such as disability and death. The syndrome of this increased vulnerability is described as frailty, and increasing fundamental evidence is emerging that suggests immunosenescence and inflammageing may underpin frailty […] Thus frailty is seen as one clinical manifestation of immunosenescence.”

The above quotes are from the book‘s preface. I gave it 3 stars on goodreads. I should probably, considering that this topic is mentioned in the preface, mention explicitly that the book doesn’t actually go into a lot of details about the downsides of ‘traditional single system based health care’; the book is mainly about immunology and related topics, and although it provides coverage of intervention studies etc., it doesn’t really provide detailed coverage about issues like the optimization of organizational structures/systems analysis etc.. The book I was currently reading while I started out writing this post – Integrated Diabetes Care – A Multidisciplinary Approach (blog coverage here) – is incidentally pretty much exclusively devoted to providing coverage of these sorts of topics (and it did a fine job).

If you have never read any sort of immunology text before the book will probably be unreadable to you – “It is aimed at fundamental scientists and clinicians with an interest in ageing or the immune system.” In my coverage below I have not made any efforts towards picking out quotes which would be particularly easy for the average reader to read and understand; this is another way of saying that the post is mainly written for my own benefit, perhaps even more so than is usually the case, not for the benefit of potential readers reading along here.

“Physiological ageing is associated with significant re-modelling of the immune system. Termed immunosenescence, age-related changes have been described in the composition, phenotype and function of both the innate and adaptive arms of the immune system. […] Neutrophils are the most abundant leukocyte in circulation […] The first step in neutrophil anti-microbial defence is their extravasation from the bloodstream and migration to the site of infection. Whilst age appears to have no effect upon the speed at which neutrophils migrate towards chemotactic signals in vitro [15], the directional accuracy of neutrophil migration to inflammatory agonists […] as well as bacterial peptides […] is significantly reduced [15]. […] neutrophils from older adults clearly exhibit defects in several key defensive mechanisms, namely chemotaxis […], phagocytosis of opsonised pathogens […] and NET formation […]. Given this near global impairment in neutrophil function, alterations to a generic signalling element rather than defects in molecules specific to each anti-microbial defence strategy is likely to explain the aberrations in neutrophil function that occur with age. In support of this idea, ageing in rodents is associated with a significant increase in neutrophil membrane fluidity, which coincides with a marked reduction in neutrophil function […] ageing results in a reduction in NK cell production and proliferation […] Numerous studies have examined the impact of age […], with the general consensus that at the single cell level, NK cell cytotoxicity (NKCC) is reduced with age […] retrospective and prospective studies have reported relationships between low NK cell activity in older adults and (1) a past history of severe infection, (2) an increased risk of future infection, (3) a reduced probability of surviving infectious episodes and (4) infectious morbidity [49–51]. Related to this increased risk of infection, reduced NKCC prior to and following influenza vaccination in older adults has been shown to be associated with reduced protective anti-hemagglutinin titres, worsened health status and an increased incidence of respiratory tract infection […] Whilst age has no effect upon the frequency or absolute number of monocytes [54, 55], the composition of the monocyte pool is markedly different in older adults, who present with an increased frequency of non-classical and intermediate monocytes, and fewer classical monocytes when compared to their younger counterparts”.

“Via their secretion of growth factors, pro-inflammatory cytokines, and proteases, senescent cells compromise tissue homeostasis and function, and their presence has been causally implicated in the development of such age-associated conditions as sarcopenia and cataracts [92]. Several studies have demonstrated a role for innate immune cells in the recognition and clearance of senescent cells […] ageing is associated with a low-grade systemic up-regulation of circulating inflammatory mediators […] Results from longitudinal-based studies suggest inflammageing is deleterious to human health with studies in older cohorts demonstrating that low-grade increases in the circulating levels of TNF-α [103], IL-6 […] and CRP [105] are associated with both all-cause […] and cause-specific […] mortality. Furthermore, inflammageing is a predictor of frailty [106] and is considered a major factor in the development of several age-related pathologies, such as atherosclerosis [107], Alzheimer’s disease [100] and sarcopenia [108].”

“Persistent viral infections, reduced vaccination responses, increased autoimmunity, and a rise in inflammatory syndromes all typify immune ageing. […] These changes can be in part attributed to the accumulation of highly differentiated senescent T cells, characterised by their decreased proliferative capacity and the activation of senescence signaling pathways, together with alterations in the functional competence of regulatory cells, allowing inflammation to go unchecked. […] Immune senescence results from defects in different leukocyte populations, however the dysfunction is most profound in T cells [6, 7]. The responses of T cells from aged individuals are typically slower and of a lower magnitude than those of young individuals […] while not all equally affected by age, the overall T cell number does decline dramatically as a result of thymic atrophy […] T cell differentiation is a highly complex process controlled not only by costimulation but also by the strength and duration of T cell receptor (TCR) signalling [34]. Nearly all TCR signalling pathways have been found altered during ageing […] two phenotypically distinct subsets of B cells […] have been demonstrated to exert immunosuppressive functions. The frequency and function of both these Breg subsets declines with age”.

“The immune impairments in patients with chronic hyperglycemia resemble those seen during ageing, namely poor control of infections and reduced vaccination response [99].” [This is hardly surprising. ‘Hyperglycemia -> accelerated ageing’ seems generally to be a good (over-)simplified model in many contexts. To give another illustrative example from Czernik & Fowlkes text, “approximately 4–6 years of diabetes exposure in some children may be sufficient to increase skin AGEs to levels that would naturally accumulate only after ~25 years of chronological aging”].

“The term “immunosenescence” is commonly taken to mean age-associated changes in immune parameters hypothesized to contribute to increased susceptibility and severity of the older adult to infectious disease, autoimmunity and cancer. In humans, it is characterized by lower numbers and frequencies of naïve T and B cells and higher numbers and frequencies of late-differentiated T cells, especially CD8+ T cells, in the peripheral blood. […] Low numbers of naïve cells render the aged highly susceptible to pathogens to which they have not been previously exposed, but are not otherwise associated with an “immune risk profile” predicting earlier mortality. […] many of the changes, or most often, differences, in immune parameters of the older adult relative to the young have not actually been shown to be detrimental. The realization that compensatory changes may be developing over time is gaining ground […] Several studies have now shown that lower percentages and absolute numbers of naïve CD8+ T cells are seen in all older subjects whereas the accumulation of very large numbers of CD8+ late-stage differentiated memory cells is seen in a majority but not in all older adults [2]. The major difference between this majority of subjects with such accumulations of memory cells and those without is that the former are infected with human herpesvirus 5 (Cytomegalovirus, CMV). Nevertheless, the question of whether CMV is associated with immunosenescence remains so far uncertain as no causal relationship has been unequivocally established [5]. Because changes are seen rapidly after primary infection in transplant patients [6] and infants [7], it is highly likely that CMV does drive the accumulation of CD8+ late-stage memory cells, but the relationship of this to senescence remains unclear. […] In CMV-seropositive people, especially older people, a remarkably high fraction of circulating CD8+ T lymphocytes is often found to be specific for CMV. However, although the proportion of naïve CD8+ T cells is lower in the old than the young whether or not they are CMV-infected, the gross accumulation of late-stage differentiated CD8+ T cells only occurs in CMV-seropositive individuals […] It is not clear whether this is adaptive or pathological […] The total CMV-specific T-cell response in seropositive subjects constitutes on average approximately 10 % of both the CD4+ and CD8+ memory compartments, and can be far greater in older people. […] there are some published data suggesting that that in young humans or young mice, CMV may improve immune responses to some antigens and to influenza virus, probably by way of increased pro-inflammatory responses […] observations suggest that the effect of CMV on the immune system may be highly dependent also on an individuals’ age and circumstances, and that what is viewed as ageing is in fact later collateral damage from immune reactivity that was beneficial in earlier life [47, 48]. This is saying nothing more than that the same immune pathology that always accompanies immune responses to acute viruses is also caused by CMV, but over a chronic time scale and usually subclinical. […] data suggest that the remodeling of the T-cell compartment in the presence of a latent infection with CMV represents a crucial adaptation of the immune system towards the chronic challenge of lifelong CMV.”

The authors take issue with using the term ‘senescence’ to describe some of the changes discussed above, because this term by definition should be employed only in the context of changes that are demonstrably deleterious to health. It should be kept in mind in this context that insufficient immunological protection against CMV in old age could easily be much worse than the secondary inflammatory effects, harmful though these may well be; CMV in the context of AIDS, organ transplantation (“CMV is the most common and single most important viral infection in solid organ transplant recipients” – medscape) and other disease states involving compromised immune systems can be really bad news (“Disease caused by human herpesviruses tends to be relatively mild and self-limited in immunocompetent persons, although severe and quite unusual disease can be seen with immunosuppression.” Holmes et al.)

“The role of CMV in the etiology of […] age-associated diseases is currently under intensive investigation […] in one powerful study, the impact of CMV infection on mortality was investigated in a cohort of 511 individuals aged at least 65 years at entry, who were then followed up for 18 years. Infection with CMV was associated with an increased mortality rate in healthy older individuals due to an excess of vascular deaths. It was estimated that those elderly who were CMV- seropositive at the beginning of the study had a near 4-year reduction in lifespan compared to those who were CMV-seronegative, a striking result with major implications for public health [59]. Other data, such as those from the large US NHANES-III survey, have shown that CMV seropositivity together with higher than median levels of the inflammatory marker CRP correlate with a significantly lower 10-year survival rate of individuals who were mostly middle-aged at the start of the study [63]. Further evidence comes from a recently published Newcastle 85+ study of the immune parameters of 751 octogenarians investigated for their power to predict survival during a 65-month follow-up. It was documented that CMV-seropositivity was associated with increased 6-year cardiovascular mortality or death from stroke and myocardial infarction. It was therefore concluded that CMV-seropositivity is linked to a higher incidence of coronary heart disease in octogenarians and that senescence in both the CD4+ and CD8+ T-cell compartments is a predictor of overall cardiovascular mortality”.

“The incidence and severity of many infections are increased in older adults. Influenza causes approximately 36,000 deaths and more than 100,000 hospitalizations in the USA every year […] Vaccine uptake differs tremendously between European countries with more than 70 % of the older population being vaccinated against influenza in The Netherlands and the United Kingdom, but below 10 % in Poland, Latvia and Estonia during the 2012–2013 season […] several systematic reviews and meta-analyses have estimated the clinical efficacy and/or effectiveness of a given influenza vaccine, taking into consideration not only randomized trials, but also cohort and case-control studies. It can be concluded that protection is lower in the old than in young adults […] [in one study including “[m]ore than 84,000 pneumococcal vaccine-naïve persons above 65 years of age”] the effect of age on vaccine efficacy was studied and the statistical model showed a decline of vaccine efficacy for vaccine-type CAP and IPD [Invasive Pneumococcal Disease] from 65 % (95 % CI 38–81) in 65-year old subjects, to 40 % (95 % CI 17–56) in 75-year old subjects […] The most effective measure to prevent infectious disease is vaccination. […] Over the last 20–30 years tremendous progress has been achieved in developing novel/improved vaccines for children, but a lot of work still needs to be done to optimize vaccines for the elderly.”

December 12, 2016 Posted by | books, diabetes, medicine | Leave a comment

Integrated Diabetes Care (I)

I’ll start out by quoting from my goodreads review of the book:

The book provides a good overview of studies and clinical trials which have attempted to improve the coordination of diabetes treatment in specific areas. The book covers research from all over the world – the UK, the US, Hong Kong, South Africa, Germany, Netherlands, Sweden, Australia. The language of the publication is quite good, considering the number of non-native English speaking contributors. An at least basic understanding of medical statistics is probably required for one to properly read and understand this book in full.

The book is quite good if you want to understand how people have tried to improve (mainly type 2) diabetes treatment ‘from an organizational point of view’ (the main focus here is not on new treatment options, but on how to optimize care delivery and make the various care providers involved work better together, in a way that improves outcomes for patients (at an acceptable cost?), which is to a large extent an organizational problem), but it’s actually also probably quite a nice book if you simply want to know more about how diabetes treatment systems differ across countries; the contributors don’t assume that the readers know how e.g. the Swedish approach to diabetes care differs from that of e.g. Pennsylvania, so many chapters contain interesting details on how specific countries/health care providers handle specific aspects of e.g. care delivery or finance.

What people mean by ‘integrated care’ varies a bit depending on whom you ask (patients and service providers may emphasize different dimensions when thinking about these topics), as should also be clear from the quotes below; however I assumed it might be a good idea to start out the post with the quote above, so that people who might have no idea what ‘integrated diabetes care’ is did not start out reading the post completely in the dark. In short, a big problem in health service delivery contexts is that care provision is often fragmented and uncoordinated, for many reasons. Ideally you might like doctors working in general practice to collaborate smoothly and efficiently with hospital staff and various other specialists involved in diabetes care (…and perhaps also with social services and mental health care providers…), but that kind of coordination often doesn’t happen, leading to what may well be sub-optimal care provision. Collaboration and a ‘desirable’ (whatever that might mean) level of coordination between service providers doesn’t happen automatically; it takes money, effort and a lot of other things (that the book covers in some detail…) to make it happen – and so often it doesn’t happen, at least there’s a lot of room for improvement even in places where things work comparatively well. Some quotes from the book on these topics:

“it is clear that in general, wherever you are in the world, service delivery is now fragmented [2]. Such fragmentation is a manifestation of organisational and financial barriers, which divide providers at the boundaries of primary and secondary care, physical and mental health care, and between health and social care. Diverse specific organisational and professional cultures, and differences in terms of governance and accountability also contribute to this fragmentation [2]. […] Many of these deficiencies are caused by organisational problems (barriers, silo thinking, accountability for budgets) and are often to the detriment of all of those involved: patients, providers and funders – in extreme cases – leading to lose-lose-lose-situations […] There is some evidence that integrated care does improve the quality of patient care and leads to improved health or patient satisfaction [10, 11], but evidence of economic benefits remain an issue for further research [10]. Failure to improve integration and coordination of services along a “care continuum” can result in suboptimal outcomes (health and cost), such as potentially preventable hospitalisation, avoidable death, medication errors and adverse drug events [3, 12, 13].”

Integrated care is often described as a continuum [10, 24], actually depicting the degree of integration. This degree can range from linkage, to coordination and integration [10], or segregation (absence of any cooperation) to full integration [25], in which the integrated organisation is responsible for the full continuum of care responsible for the full continuum of care […] this classification of integration degree can be expanded by introducing a second dimension, i.e., the user needs. User need should be defined by criteria, like stability and severity of condition, duration of illness (chronic condition), service needed and capacity for self-direction (autonomy). Accordingly, a low level of need will not require a fully integrated system, then [10, 24] […] Kaiser Permanente is a good example of what has been described as a “fully integrated system. […] A key element of Kaiser Permanente’s approach to chronic care is the categorisation of their chronically ill patients into three groups based on their degree of need“.

It may be a useful simplification to think along the lines of: ‘Higher degree of need = a higher level of integration becomes desirable/necessary. Disease complexity is closely related to degree of need.’ Some related observations from the book:

“Diabetes is a condition in which longstanding hyperglycaemia damages arteries (causing macrovascular, e.g., ischaemic heart, peripheral and cerebrovascular disease, and microvascular disease, e.g., retinopathy, nephropathy), peripheral nerves (causing neuropathy), and other structures such as skin (causing cheiroarthropathy) and the lens (causing cataracts). Different degrees of macrovascular, neuropathic and cutaneous complications lead to the “diabetic foot.” A proportion of patients, particularly with type 2 diabetes have metabolic syndrome including central adiposity, dyslipidaemia, hypertension and non alcoholic fatty liver disease. Glucose management can have severe side effects, particularly hypoglycaemia and weight gain. Under-treatment is not only associated with long term complications but infections, vascular events and increased hospitalisation. Absence of treatment in type 1 diabetes can rapidly lead to diabetic keto-acidosis and death. Diabetes doubles the risk for depression, and on the other hand, depression may increase the risk for hyperglycaemia and finally for complications of diabetes [41]. Essentially, diabetes affects every part of the body once complications set in, and the crux of diabetes management is to normalise (as much as possible) the blood glucose and manage any associated risk factors, thereby preventing complications and maintaining the highest quality of life. […] glucose management requires minute by minute, day by day management addressing the complexity of diabetes, including clinical and behavioural issues. While other conditions also have the patient as therapist, diabetes requires a fully empowered patient with all of the skills, knowledge and motivation every hour of the waking day. A patient that is fully engaged in self-management, and has support systems, is empowered to manage their diabetes and will likely experience better outcomes compared with those who do not have access to this support. […] in diabetes, the boundaries between primary care and secondary care are blurred. Diabetes specialist services, although secondary care, can provide primary care, and there are GPs, diabetes educators, and other ancillary providers who can provide a level of specialist care.”

In short, diabetes is a complex disease – it’s one of those diseases where a significant degree of care integration is likely to be necessary in order to achieve even close to optimal outcomes. A little more on these topics:

“The unique challenge to providers is to satisfy two specific demands in diabetes care. The first is to anticipate and recognize the onset of complications through comprehensive diabetes care, which demands meticulous attention to a large number of process-of-care measures at each visit. The second, arguably greater challenge for providers is to forestall the development of complications through effective diabetes care, which demands mastery over many different skills in a variety of distinct fields in order to achieve performance goals covering multiple facets of management. Individually and collectively, these dual challenges constitute a virtually unsustainable burden for providers. That is because (a) completing all the mandated process measures for comprehensive care requires far more time than is traditionally available in a single patient visit; and (b) most providers do not themselves possess skills in all the ancillary disciplines essential for effective care […] Diabetes presents patients with similarly unique dual challenges in mastering diabetes self-management with self-awareness, self-empowerment and self-confidence. Comprehensive Diabetes Self-Management demands the acquisition of a variety of skills in order to fulfil a multitude of tasks in many different areas of daily life. Effective Diabetes Self-Management, on the other hand, demands constant vigilance, consistent discipline and persistent attention over a lifetime, without respite, to nutritional self-discipline, monitoring blood glucose levels, and adherence to anti-diabetic medication use. Together, they constitute a burden that most patients find difficult to sustain even with expert assistance, and all-but-impossible without it.”

“Care coordination achieves critical importance for diabetes, in particular, because of the need for management at many different levels and locations. At the most basic level, the symptomatic management of acute hypo- and hyperglycaemia often devolves to the PCP [primary care provider], even when a specialist oversees more advanced strategies for glycaemic management. At another level, the wide variety of chronic complications requires input from many different specialists, whereas hospitalizations for acute emergencies often fall to hospitalists and critical care specialists. Thus, diabetes care is fraught with the potential for sometimes conflicting, even contradictory management strategies, making care coordination mandatory for success.”

“Many of the problems surrounding the provision of adequate person-centred care for those with diabetes revolve around the pressures of clinical practice and a lack of time. Good diabetes management requires attention to a number of clinical parameters
1. (Near) Normalization of blood glucose
2. Control of co-morbidities and risk factors
3. Attainment of normal growth and development
4. Prevention of Acute Complications
5. Screening for Chronic Complications
To fit all this and a holistic, patient-centred collaborative approach into a busy general practice, the servicing doctor and other team members must understand that diabetes cannot be “dealt with” coincidently during a patient consultation for an acute condition.”

“Implementation of the team model requires sharing of tasks and responsibilities that have traditionally been the purview of the physician. The term “team care” has traditionally been used to indicate a group of health-care professionals such as physicians, nurses, pharmacists, or social workers, who work together in caring for a group of patients. In a 2006 systematic review of 66 trials testing 11 strategies for improving glycaemic control for patients with diabetes, only team care and case management showed a significant impact on reducing HbA1c levels [18].”

Moving on, I found the chapter about Hong Kong interesting, for several reasons. The quality of Scandinavian health registries are probably widely known in the epidemiological community, but I was not aware of Hong Kong’s quality of diabetes data, and data management strategies, which seems to be high. Nor was I aware of some of the things they’ve discovered while analyzing those data. A few quotes from that part of the coverage:

“Given the volume of patients in the clinics, the team’s earliest work from the HKDR [Hong Kong Diabetes Registry, US] prioritized the development of prediction models, to allow for more efficient, data-driven risk stratification of patients. After accruing data for a decade on over 7000 patients, the team established 5-year probabilities for major diabetes-related complications as defined by the International Code for Diseases retrieved from the CMS [Clinical Management System, US]. These included end stage renal disease [7], stroke [8], coronary heart disease [9], heart failure [10], and mortality [11]. These risk equations have a 70–90 % sensitivity and specificity of predicting outcomes based on the parameters collected in the registry.”

“The lifelong commitments to medication adherence and lifestyle modification make diabetes self-management both physically and emotionally taxing. The psychological burdens result from insulin injection, self-monitoring of blood glucose, dietary restriction, as well as fear of complications, which may significantly increase negative emotions in patients with diabetes. Depression, anxiety, and distress are prevalent mental afflictions found in patients with diabetes […] the prevalence of depression was 18.3 % in Hong Kong Chinese patients with type 2 diabetes. Furthermore, depression was associated with poor glycaemic control and self-reported hypoglycaemia, in part due to poor adherence […] a prospective study involving 7835 patients with type 2 diabetes without cardiovascular disease (CVD) at baseline […] found that [a]fter adjusting for conventional risk factors, depression was independently associated with a two to threefold increase in the risk of incident CVD [22].”

“Diabetes has been associated with increased cancer risk, but the underlying mechanism is poorly understood. The linkage between the longitudinal clinical data within the HKDR and the cancer outcome data in the CMS has provided important observational findings to help elucidate these connections. Detailed pharmacoepidemiological analyses revealed attenuated cancer risk in patients treated with insulin and oral anti-diabetic drugs compared with non-users of these drugs”

“Among the many challenges of patient self-management, lack of education and empowerment are the two most cited barriers [59]. Sufficient knowledge is unquestionably important in self-care, especially in people with low health literacy and limited access to diabetes education. Several systematic reviews [have] showed that self-management education with comprehensive lifestyle interventions improved glycaemic and cardiovascular risk factor control [60–62].”

“Clinical trials are expensive because of the detail and depth of data required on each patient, which often require separate databases to be developed outside of the usual-care electronic medical records or paper-based chart systems. These databases must be built, managed, and maintained from scratch every time, often requiring double-entry of data by research staff. The JADE [Joint Asia Diabetes Evaluation] programme provides a more efficient means of collecting the key clinical variables in its comprehensive assessments, and allows researchers to add new fields as necessary for research purposes. This obviates the need for redundant entry into non-clinical systems, as the JADE programme is simultaneously a clinical care tool and prospective database. […] A large number of trials fail because of inadequate recruitment [67]. The JADE programme has allowed for ready identification of eligible clinical trial participants because of its detailed clinical database. […] One of the greatest challenges in clinical trials is maintaining the contact between researchers and patients over many years. […] JADE facilitates long-term contact with the patient, as part of routine periodic follow-up. This also allows researchers to evaluate longer term outcomes than many previous trials, given the great expense in maintaining databases for the tracking of longitudinal outcomes.”

Lastly, some stuff on cost and related matters from the book:

“Diabetes imposes a massive economic burden on all healthcare systems, accounting for 11 % of total global healthcare expenditure on adults in 2013.”

“Often, designated service providers institute managed care programmes to standardize and control care rendered in a safe and cost-effective manner. However, many of these programmes concentrate on cost-savings rather than patient service utilization and improved clinical outcomes. [this part of the coverage is from South Africa, but these kinds of approaches are definitely not limited to SA – US] […] While these approaches may save some costs in the short-term, Managed Care Programmes which do not address patient outcomes nor reduce long term complications, ignore the fact that that the majority of the costs for treating diabetes, even in the medium term, are due to the treatment of acute and chronic complications and for inpatient hospital care [14]. Additionally, it is well established that poor long-term clinical outcomes increase the cost burden of managing the patient with diabetes by up to 250 %. […] overall, the costs of medication, including insulin, accounts for just 7 % of all healthcare costs related to diabetes [this number varies across countries, I’ve seen estimates of 15% in the past – and as does the out-pocket share of that cost – but the costs of medications constitute a relatively small proportion of the total costs of diabetes everywhere you look, regardless of health care system and prevalence. If you include indirect costs as well, which you should, this becomes even more obvious – US]”

“[A] study of the Economic Costs of Diabetes in the U.S. in 2012 [25] showed that for people with diabetes, hospital inpatient care accounted for 43 % of the total medical cost of diabetes.”

“There is some evidence of a positive impact of integrated care programmes on the quality of patient care [10, 34]. There is also a cautious appraisal that warns that “Even in well-performing care groups, it is likely to take years before cost savings become visible” […]. Based on a literature review from 1996 to 2004 Ouwens et al. [11] found out that integrated care programmes seemed to have positive effects on the quality of care. […] because of the variation in definitions of integrated care programmes and the components used cover a broad spectrum, the results should be interpreted with caution. […] In their systematic review of the effectiveness of integrated care Ouwens et al. [11] could report on only seven (about 54 %) reviews which had included an economic analysis. Four of them showed financial advantages. In their study Powell Davies et al. [34] found that less than 20 % of studies that measured economic outcomes found a significant positive result. Similarly, de Bruin et al. [37] evaluated the impact of disease management programmes on health-care expenditures for patients with diabetes, depression, heart failure or chronic obstructive pulmonary disease (COPD). Thirteen studies of 21 showed cost savings, but the results were not statistically significant, or not actually tested for significance. […] well-designed economic evaluation studies of integrated care approaches are needed, in particular in order to support decision-making on the long-term financing of these programmes [30, 39]. Savings from integrated care are only a “hope” as long as there is no carefully designed economic analysis with a kind of full-cost accounting.”

“The cost-effectiveness of integrated care for patients with diabetes depends on the model of integrated care used, the system in which it is used, and the time-horizon chosen [123]. Models of cost benefit for using health coaching interventions for patients with poorly controlled diabetes have generally found a benefit in reducing HbA1c levels, but at the cost of paying for the added cost of health coaching which is not offset in the short term by savings from emergency department visits and hospitalizations […] An important question in assessing the cost of integrated care is whether it needs to be cost-saving or cost-neutral to be adopted, or is it enough to increase quality-adjusted life years (QALYs) at a “reasonable” cost (usually pegged at between $30,000 and $60,000 per QALY saved). Most integrated care programmes for patients with diabetes that have been evaluated for cost-effectiveness would meet this more liberal criterion […] In practice, integrated care programmes for patients with diabetes are often part of generalized programmes of care for patients with other chronic medical conditions, making the allocation of costs and savings with respect to integrated care for diabetes difficult to estimate. At this point, integrated care for patients with diabetes appears to be a widely accepted goal. The question becomes: which model of integrated care is most effective at reasonable cost? Answering this question depends both on what costs are included and what outcomes are measured; the answers may vary among different patient populations and different care systems.”

December 6, 2016 Posted by | books, diabetes, economics, medicine | 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 | books, cancer, diabetes, genetics, medicine, Neurology, Pharmacology | Leave a comment

Diabetic nephropathies

Bakris et al.‘s text on this topic is the first book I’ve read specifically devoted to the topic of DN. As I pointed out on goodreads, “this is a well-written and interesting work which despite the low page count cover quite a bit of ground. A well-sourced and to-the-point primer on these topics.” Below I have added a few observations from the book.

“Diabetic nephropathy (DN), also known as diabetic kidney disease (DKD), is one of the most important long-term complications of diabetes and the most common cause of endstage renal disease (ESRD) worldwide. DKD […] is defined as structural and functional renal damage manifested as clinically detected albuminuria in the presence of normal or abnormal glomerular filtration rate (GFR). […] Patients with DKD […] account for one-third of patients demanding renal transplantation. […] in the United States, Medicare expenditure on treating ESRD is approximately US $33 billion (as of 2010), which accounts for 8–9 % of the total annual health-care budget […] According to the United States Renal Data System […], the incidence of ESRD requiring RRT [in 2012] was 114,813 patients, with 44 % due to DKD [9]. A registry report from Japan revealed a nearly identical relative incidence, with 44.2 % of the patients with ESRD caused by diabetes”

Be careful not to confuse incidence and prevalence here; the proportion of diabetics diagnosed with ESDR in any given year is almost certainly higher than the proportion of people with ESDR who have diabetes, because diabetics with kidney failure die at a higher rate than do other people with kidney failure. This problem/fact tends to make some questions hard to answer; to give an example, how large a share of the total costs that diabetics contribute to the whole kidney disease component of medical costs seems to me to be far from an easy question to answer, because you in some sense are not really making an apples-to-apples comparison, and a lot might well depend on the chosen discount rate and how to address the excess mortality in the diabetes sample; and even ‘simply’ adding up medical outlays for the diabetes- and non-diabetes samples would require a lot of data (which may not be available) and work. You definitely cannot just combine the estimates provided above, and assume that the 44% incidence translates into 44% of people with ESDR having diabetes; it’s not clear in the text where the ‘one-third of patients’ number above comes from, but if that’s also US data then it should be obvious from the difference between these numbers that there’s a lot of excess mortality here in the diabetes sample (I have included specific data from the publication on these topics below). The book also talks about the fact that the type of dialysis used in a case of kidney failure will to some extent depend on the health status of the patient, and that diabetes is a significant variable in that context; this means that the available/tolerable treatment options for the kidney disease component may not be the same in the case of a diabetic and a case of a patient with, say, lupus nephritis, and it also means that the patient groups most likely are not ‘equally sick’, so basing cost estimates on cost averages might lead to misleading results if severity of disease and (true) treatment costs are related, as they usually are.

“A recent analysis revealed an estimated diabetes prevalence of 12–14 % among adults in the United States […] In the age group ≥65 years, this amounts to more than 20 %”.

It should be emphasized in the context of the above numbers that the prevalence of DKD is highly variable across countries/populations – the authors also include in the book the observation that: “Over a period of 20 years, 32 studies from 16 countries revealed a prevalence ranging from 11 to 83 % of patients with diabetes”. Some more prevalence data:

“DKD affects about 30 % of patients with type 1 diabetes and 25–40 % of the patients with type 2 diabetes. […] The global prevalence of micro- and macroalbuminuria is estimated at 39 % and 10 %, respectively […] (NHANES III) […] reported a prevalence of 35 % (microalbuminuria) and 6 % (macroalbuminuria) in patients with T2DM aged ≥40 years [24]. In another study, this was reported to be 43 % and 12 %, respectively, in a Japanese population [23]. According to the European Diabetes (EURODIAB) Prospective Complications Study Group, in patients with T1DM, the incidence of microalbuminuria was 12.6 % (over 7.3 years) [25]. This prevalence was further estimated at 33 % in an 18-year follow-up study in Denmark […] In the United Kingdom Prospective Diabetes Study (UKPDS), proteinuria [had] a peak incidence after around 15–20 years after diabetes diagnosis.”

I won’t cover the pathophysiology parts in too much detail here, but a few new things I learned does need to be mentioned:

“A natural history of DKD was first described in the 1970s by Danish physicians [32]. It was characterized by a long silent period without overt clinical signs and symptoms of nephropathy and progression through various stages, starting from hyperfiltration, microalbuminuria, macroalbuminuria, and overt renal failure to ESRD. Microalbuminuria (30–300 mg/day of albumin in urine) is a sign of early DKD, whereas macroalbuminuria (>300 mg/day) represents DKD progression. [I knew this stuff. The stuff that follows below was however something I did not know:]
However, this ‘classical’ natural evolution of urinary albumin excretion and change in GFR is not present in many patients with diabetes, especially those with type 2 diabetes [34]. These patients can have reduction or disappearance of proteinuria over time or can develop even overt renal disease in the absence of proteinuria [30, 35]. […] In the Wisconsin Epidemiologic Study of Diabetic Retinopathy (WESDR) of patients with T2DM, 45.2 % of participants developed albuminuria, and 29 % developed renal impairment over a 15-year follow-up period [37]. Of those patients who developed renal impairment, 61 % did not have albuminuria beforehand, and 39 % never developed albuminuria during the study. Of the patients that developed albuminuria, only 24 % subsequently developed renal impairment during the study. A significant degree of discordance between development of albuminuria and renal impairment is apparent [37]. These data, thus, do not support the classical paradigm of albuminuria always preceding renal impairment in the progression of DKD. […] renal hyperfiltration and rapid GFR decline are considered stronger predictors of nephropathy progression in type 1 diabetes than presence of albuminuria [67]. The annual eGFR loss in patients with DKD is >3 mL/min/1.73 m2 or 3.3 % per year.”

As for the last part about renal hyperfiltration, they however also note later in the coverage in a different chapter that “recent long-term prospective surveys cast doubt on the validity of glomerular hyperfiltration being predictive of renal outcome in patients with type 1 diabetes”. Various factors mentioned in the coverage – some of which are very hard to avoid and some of which are actually diabetes-specific – contribute to measurement error, which may be part of the explanation for the sub-optimal performance of the prognostic markers employed.

An important observation I think I have mentioned before here on the blog is that diabetic nephropathy is not just bad because people who develop this complication may ultimately develop kidney failure, but is also bad because diabetics may die before they even do that; diabetics with even moderate stages of nephropathy have high mortality from cardiovascular disease, so if you only consider diabetics who actually develop kidney failure you may miss some of the significant adverse health effects of this complication; it might be argued that doing this would be a bit like analyzing the health outcomes of smokers while only tallying the cancer cases, and ignoring e.g. the smoking-associated excess deaths from cardiovascular disease. Some observations from the book on this topic:

“Comorbid DM and DKD are associated with high cardiovascular morbidity and mortality. The risk of cardiovascular disease is disproportionately higher in patients with DKD than patients with DM who do not have kidney disease [76]. The incident dialysis rate might even be higher after adjusting for patients dying from cardiovascular disease before reaching ESRD stage [19]. The United States Renal Data System (USRDS) data shows that elderly patients with a triad of DM, chronic kidney disease (CKD), and heart failure have a fivefold higher chance of death than progression to CKD and ESRD [36]. The 5-year survival rate for diabetic patients with ESRD is estimated at 20 % […] This is higher than the mortality rate for many solid cancers (including prostate, breast, or renal cell cancer). […] CVD accounts for more than half of deaths of patients undergoing dialysis […] the 5-year survival rate is much lower in diabetic versus nondiabetic patients undergoing hemodialysis […] Adler et al. tested whether HbA1c levels were associated with death in adults with diabetes starting HD or peritoneal dialysis [38]. Of 3157 patients observed for a median time of 2.7 years, 1688 died. [this example provided, I thought, a neat indication of what sort of data you end up with when you look at samples with a 20% 5-year survival rate] […] Despite modern therapies […] most patients continue to show progressive renal damage. This outcome suggests that the key pathogenic mechanisms involved in the induction and progression of DN remain, at least in part, active and unmodified by the presently available therapies.” (my emphasis)

The link between blood glucose (Hba1c) and risk of microvascular complications such as DN is strong and well-documented, but Hba1c does not explain everything:

“Only a subset of individuals living with diabetes […] develop DN, and studies have shown that this is not just due to poor blood glucose control [50–54]. DN appears to cluster in families […] Several consortia have investigated genetic risk factors […] Genetic risk factors for DN appear to differ between patients with type 1 and type 2 diabetes […] The pathogenesis of DN is complex and has not yet been completely elucidated […] [It] is multifactorial, including both genetic and environmental factors […]. Hyperglycemia affects patients carrying candidate genes associated with susceptibility to DN and results in metabolic and hemodynamic alterations. Hyperglycemia alters vasoactive regulators of glomerular arteriolar tone and causes glomerular hyperfiltration. Production of AGEs and oxidative stress interacts with various cytokines such as TGF-β and angiotensin II to cause kidney damage. Additionally, oxidative stress can cause endothelial dysfunction and systemic hypertension. Inflammatory pathways are also activated and interact with the other pathways to cause kidney damage.”

“An early clinical sign of DN is moderately increased urinary albumin excretion, referred to as microalbuminuria […] microalbuminuria has been shown to be closely associated with an increased risk of cardiovascular morbidity and mortality [and] is [thus] not only a biomarker for the early diagnosis of DN but also an important therapeutic target […] Moderately increased urinary albumin excretion that progresses to severely increased albuminuria is referred to as macroalbuminuria […] Severely increased albuminuria is defined as an ACR≥300 mg/g Cr; it leads to a decline in renal function, which is defined in terms of the GFR [8] and generally progresses to ESRD 6–8 years after the onset of overt proteinuria […] patients with type 1 diabetes are markedly younger than type 2 patients. The latter usually develop ESRD in their mid-fifties to mid-sixties. According to a small but carefully conducted study, both type 1 and type 2 patients take an average of 77–81 months from the stage of producing macroproteinuria with near-normal renal function to developing ESRD [17].”

“Patients with diabetes and kidney disease are at increased risk of hypoglycemia due to decreased clearance of some of the medications used to treat diabetes such as insulin, as well as impairment of renal gluconeogenesis from having a lower kidney mass. As the kidney is responsible for about 30–80 % of insulin removal, reduced kidney function is associated with a prolonged insulin half-life and a decrease in insulin requirements as estimated glomerular filtration rate (eGFR) decline […] Metformin [a first-line drug for treating type 2 diabetes, US] should be avoided in patients with an eGFR < 30 mL/min /1.73 m2. It is recommended that metformin is stopped in the presence of situations that are associated with hypoxia or an acute decline in kidney function such as sepsis/shock, hypotension, acute myocardial infarction, and use of radiographic contrast or other nephrotoxic agents […] The ideal medication regimen is based on the specific needs of the patient and physician experience and should be individualized, especially as renal function changes. […] Lower HbA1c levels are associated with higher risks of hypoglycemia so the HbA1c target should be individualized […] Whereas patients with mild renal insufficiency can receive most antihyperglycemic treatments without any concern, patients with CKD stage 3a and, in particular, with CKD stages 3b, 4, and 5 often require treatment adjustments according to the degree of renal insufficiency […] Higher HbA1c targets should be considered for those with shortened life expectancies, a known history of severe hypoglycemia or hypoglycemia unawareness, CKD, and children.”

“In cases where avoidance of development of DKD has failed, the second approach is slowing disease progression. The most important therapeutic issues at this stage are control of hypertension and hyperglycemia. […] Hypertension is present in up to 85 % of patients with DN/ DKD, depending on the duration and stage (e.g., higher in more progressive cases). […] In a recent meta-analysis, the efficacy and safety of blood pressure-lowering agents in adults with diabetes and kidney disease was analyzed […] In total, 157 studies comprising 43,256 participants, mostly with type 2 diabetes and CKD, were included in the network meta-analysis. No drug regimen was found to be more effective than placebo for reducing all-cause mortality. […] DKD is accompanied by abnormalities in lipid metabolism related to decline in kidney function. The association between higher low-density lipoprotein cholesterol (LDL-C) and risk of myocardial infarction is weaker for people with lower baseline eGFR, despite higher absolute risk of myocardial infarction [53]. Thus, increased LDL-C seems to be less useful as a marker of coronary risk among people with CKD than in the general population.”

“An analysis of the USRDS data revealed an RR of 0.27 (95 % CI, 0.24–0.30) 18 months after transplantation in patients with diabetes in comparison to patients on dialysis on a transplant waiting list [76]. The gain in projected years of life with transplantation amounted to 11 years in patients with DKD in comparison to patients without transplantation.”

October 27, 2016 Posted by | books, diabetes, medicine, Pharmacology | Leave a comment

Human Drug Metabolism (III)

This is my third post about this book. You can read my previous posts here and here. In this post I have covered material from chapter 7, dealing with ‘factors affecting drug metabolism’.

“Data from animal studies in one country are usually comparable with that of another, provided the animal species and strain are the same. This provides a consistent picture of the basic pharmacological and toxicological actions of a candidate drug in a living organism […] it has been obvious since animal testing began that there would be large differences in the way a drug might perform in man compared with animal species […]. Unfortunately, there is no experimental model yet designed that can not only consider human biochemistry and physiology, but also the effects of age, smoking, legal and illegal drug usage, gender, diet, environment, disease and finally genetic variation. Indeed, many clinical studies have revealed enormous differences in drug clearance and pharmacological effect even in age, sex and ethnically matched individuals. In effect, this means that the first year or so of a drug’s clinical life is a vast, but monitored experiment, involving hundreds of thousands of patients and there is no guarantee of success.”

“Most biotransformational polymorphisms that might potentially cause a problem clinically are due to an inability of those with defective enzymes to remove the drug from the system. Drug failure can occur if the agent is administered as a pro-drug and requires some metabolic conversion to an active metabolite. Drug accumulation can lead to unpleasant side effects and loss of patient tolerance for the agent. […] Overall, there are a large number of factors that can influence drug metabolism, either by increasing clearance to cause drug failure, or by preventing clearance to lead to toxicity. In the real world, it is often impossible to delineate the different conflicting factors which result in net changes in drug clearance which cause a drug to fall out of, or climb above, the therapeutic window. It may only be possible clinically in many cases to try to change what appears to be the major cause to bring about a resolution of the situation to restore curative and non-toxic drug levels.”

“Most population studies of human polymorphisms list the allelic frequency, that is, how many of an ethnic group contain the alleles in question. […] The actual haplotypes in the population, that is, which individuals express which combinations of alleles, are not the same as the population allelic frequency. […] If an SNP or a combination of SNPs is a fairly mild defect in the enzyme when it is homozygously expressed, then the heterozygotes will show little impairment and the polymorphism may be clinically irrelevant. With other SNPs, the enzyme produced may be completely non-functional.  Homozygotes will be virtually unable to clear the drug and heterozygotes will show impairment also. There are also smaller populations of UMs, or ultra rapid metabolizers which may have a feature of their enzyme which either makes it super efficient or expressed in abnormally high amounts. […] Phenotyping will group patients in very broad EMs [extensive metabolizers], IMs [intermediate metabolizers] or PM [poor metabolizers] categories, but will be unable to distinguish between heterozygous and homozygous EMs. Although genotyping may be very helpful in dosage estimation in the initiation of therapy, there is no substitute for the normal process of therapeutic monitoring, which is effectively phenotyping the individual in the real world in terms of maximizing response and minimizing toxicity.”

“it is clear that there is a vast amount of genetic variation across humanity in terms of biotransformational capability and so the idea that in therapeutics, ‘one size fits all’ is not only outdated, but fabulously naïve. […] Unfortunately, detecting and responding successfully to human biotransformational polymorphisms has proved to be extremely problematic. In terms of polymorphism detection, this area is a classic illustration of how the exploration of the human genome with powerful molecular biological tools may unearth many apparently marked polymorphic defects that may not necessarily translate into a measurable clinical impact in terms of efficacy and toxicity. In reality, many more scientists have the opportunity to discover and publish such polymorphisms in vitro, than there are clinical scientists, resources and indeed cooperative volunteers or patients in sufficient quantity to determine practical clinical relevance.”

the CYP3A group (chromosome 7) metabolize around half of all drugs […] variation in the metabolism of CYP3A substrates […] can be up to ten-fold in terms of drug clearances and up to 90-fold in liver protein expression. […] It is likely that the full extent of the variation in CYP3A4 is still to be discovered […] While it is thought that CYP3A4 is not subject to an obvious major polymorphism, CYP3A5 definitely is. […] *3/*3 individuals form no serviceable CYP3A5. Functional CYP3A5 is found in around 20 per cent of Caucasians, half of Chinese/Japanese, 70 per cent of Hispanics and more than 80 per cent of African Americans.”

“A particularly dangerous polymorphism clinically was identified in the 1980s for one of the methyltransferases. The endogenous role of S-methylating thiopurine S-methyltransferase (TPMT) is not that clear, but […] [t]hese drugs are […] effective in some childhood leukaemias […] TPMT highlights the genotyping/phenotyping issue mentioned earlier in the management of patients with polymorphisms. Genotyping will reveal the level of TPMT expression that should be expected in the otherwise healthy patient. However, there are many factors which impact day-to-day TPMT expression during thiopurine therapy. […] Hence, what might be predicted from a genotype test may bear little resemblance to how the enzyme is performing on a particular day in a treatment cycle. So clinically, it is preferred to test actual TPMT activity.”

“Understanding of sulphonation and its roles in endogenous as well as xenobiotic metabolism is not as advanced compared with that of CYPs; however, the role of SULTs in the activation of carcinogens is becoming more apparent. One of the major influences on SULT activity is their polymorphic nature; in the case of one of the most important toxicologically relevant SULTs, SULT1A1, this isoform exists as three variants, SULT1A1*1 (wild-type), SULT1A1*2 and SULT1A1*3. The *1 variant allele is found in the majority of Caucasians (around 65 per cent), whilst the *2 variant differs only in the exchange of one amino acid for another. This single amino acid change has profound effects on the stability and catalytic activity of the isoform. The *2 variant is found in approximately 32 per cent of Caucasians and catalytically faulty […] About 9 in 10 Chinese people have the *1 allele and about 8 per cent have allele *2. About half of African-Americans have *1 and a third have *2. Interestingly, there is a *3 which is rare in most races but accounts for more than 22 per cent of African Americans. There is also considerable variation in SULT2A1 and SULT2B1, which are the major hydroxysteroid sulphators in the body, which may have implications for sex steroid and cholesterol handling. […] from the cancer-risk viewpoint, a highly active SULT1A1 *1 is usually an advantage in that it usually removes reactive species rapidly as stable sulphates. With some agents it is problematic as certain carcinogens such as acetylfluorene are indirectly activated to reactive species by SULTs. In addition, protective dietary flavonoids […] are also rapidly cleared by SULT1A1 *1, so there is a combination of production of toxins and loss of protective dietary agents. In terms of carcinogenesis risk, SULT1A1*2 could be a liability as potentially damaging substrates such as electrophilic toxins cannot be cleared rapidly. However, in some circumstances the *2 allele can be rather protective as […] it also allows protective agents [to] remain in tissues for longer periods. The combinations are endless and so it is often extremely difficult to predict risks of carcinogenicity for individuals and toxin exposures.”

GSTs are polymorphic and much research has been directed at linking increased predisposition to cytotoxicity and carcinogenicity with defective GST phenotypes. Active wild-type GSTMu-1 is found in around 60 per cent of Caucasians, but a non-functional version of the isoform is found in the remainder. […] GST-M1 null (non-functional alleles) can predispose to risks of prostate abnormalities and GST Pi is subject to several SNPs and many attempts have been made to link these SNPs with the consequences of failure to detoxify reactive species, such as the risk of lung cancer. […] Carcinogenesis may be due to a complex mix of factors, where different enzyme expression and activities may combine with particular reactive species from specific parent xenobiotics that lead to DNA damage only in certain individuals. Resolving specific risk factors may be extremely difficult in such circumstances. […] in cancer chemotherapy, there is evidence that the presence of GST-M1 and GST-T1 null (non-functional) alleles predisposes children to a six-fold higher level of adverse events usually seen with antineoplastic drugs, such as bone marrow damage, nephrotoxicity and neurotoxicity.”

“The effects of age on drug clearance and metabolism have been known since the 1950s, but they have been extensively investigated in the last 20 or so years. It is now generally accepted that at the extremes of life, neonatal and geriatric, drug clearance can be significantly different from the rest of humanity. In general, neonates, i.e. those less than four weeks old, cannot clear certain agents due to immaturity of drug metabolizing systems. Those over retirement age cannot clear the drugs due to loss of efficiency in their metabolizing systems. Either way, the net result can be toxicity due to drug accumulation. […] It seems that the inability of older people to clear drugs is not necessarily related to the efficacy of their CYP-mediated oxidations, which are often not much different from that of younger individuals. Studies with the major CYPs in vitro have revealed that CYP2D6 is unaffected by age, as are most other CYPs, with the exception of CYP1A2, which does decline in activity in the elderly. […] In general, there is little significant change in the inducibility in most CYPs, or in the capability of conjugation systems in vitro. […] there are significant changes in the liver itself, as it decreases in mass and its blood flow is reduced as we age. This occurs at the rate of around 0.5–1.5 per cent per year, so by the time we hit 60–70, we may have up to a 40 per cent decline in liver blood flow compared with a 30-year-old. Other factors include gradual decline in renal function, increased fat deposits and reduction in gut blood flow, which affects absorption. […] The problem arises that the drug’s bioavailability increases due to lack of first-pass clearance; this means that from a standard dose, blood levels can be considerably higher than would be expected in a 40-year-old. This can be a serious problem in drugs with a narrow TI, such as antiarrhythmics. In addition, average doses of warfarin required to provide therapeutic anticoagulation in the elderly are less than half those required for younger people. The person’s lifelong smoking and drinking habits, as well as older individuals ’ sometimes erratic diet also complicate this situation. Among the drugs cleared more slowly in older people are antipsychotics, paracetamol, antidepressants, benzodiazepines, warfarin, beta-blockers and indomethicin.”

“Thousands of polyphenols are found in plants, vegetables, fruit, as well as tea, coffee, wine and fruit juices. […] Flavonoids such as quercetin and fisetin are excellent substrates for COMT, so competitively inhibiting the metabolism of endogenous catecholamine and catechol oestrogens. Quercetin and other polyphenols are found in various foods such as soy (genestein) and they are potent inhibitors of SULT1A1 which sulphate endogenous oestrogens, so potentiating the effects of oestrogens in the body. Many of these flavonoids and isoflavonoids are manufactured and sold as cancer preventative agents; however, it is more likely that their elevation of oestrogen levels may have the opposite effect in the long term. It is also likely that various polyphenols influence other endogenous substrates of sulphotransferases, such as thyroid hormones and various catecholamines. It is gradually becoming apparent that polyphenols can induce UGTs, indeed; it would be surprising if they did not. […] Overall, it is likely that there are a large number of polyphenols that are potent modulators of CYPs and conjugative enzymes. […] It is clear that diet can substantially modulate biotransformation […] As to the effects on prescription drugs, […] abrupt changes in a person’s diet may significantly alter the clearance of drugs and lead to loss of efficacy or toxicity.”

In general, experimental or ‘probe’ drugs […] which are used to study the activities of a number of CYPs, are metabolized more quickly by women than men. This is allowing for differences in weight, fat distribution (body mass index) and volume of distribution […] It appears that CYP expression is linked to growth hormone (GH) and about the same amount is secreted over 24 hours in both sexes. In animals the pattern of release of the hormone is crucial to the effects on the CYPs; in females, GH is secreted in small but more or less continuous pulses, while males secrete large pulses, then periods of no secretion. The system is thought to be similar in humans. […] Little is known of the effects of the menopause and hormone replacement, where steroid metabolism changes dramatically. It is highly likely that these events could have profound effects on female drug clearance. […] females in general are more susceptible to drug adverse reactions than males, especially hepatotoxic effects.”

“For those chronically dependent on ethanol their CYP2E1 levels can be ten-fold higher than non-drinkers and they would clear CYP2E1 substrates extremely quickly if they chose to be sober for a period of time. This may lead to the accumulation of metabolites of the substrates. It is apparent that alcoholics who are sober can suffer paracetamol (acetaminophen)-induced liver toxicity at overdoses of around half that of non-drinkers, which is due to CYP2E1 induction. […]  the vast variation in ADH [alcohol dehydrogenase] catalytic activity across the human race is mainly due to just a few SNPs that profoundly change the efficiency of the isoforms. ADH1B/*1 is the most effective variant and is the ADH wild-type […] Part of a ‘successful’ career as an alcoholic depends possessing the ADH1B/*1 isoform. The other defective isoforms are found in low frequencies in alcoholics and cirrhotics. […] in the vast majority of individuals, whatever their variant of ADH, they are able to process acetaldehyde to acetate and water, as the consequences of failing to do this are severe. With ALDH, the wild-type and gold standard is ALDH2*1/*1, which has the highest activity of all these isoforms and is the second essential component for an alcoholic career. […] the variant ALDH2*1/*2 has less than a quarter of the wild-type’s capacity and is found predominantly in Eastern races. The variant ALDH2*2/*2 is completely useless and renders the individuals very sensitive to acetaldehyde poisoning, although the toxin is removed eventually by ALDH1A1 which does not seem to be affected by polymorphisms. In a survey of 1300 Japanese alcoholics, there was nobody at all with the ALDH2*2/*2 variant. […] Women are much more vulnerable to ethanol damage and on average die in half the time it generally takes for a male alcoholic to drink himself to death. Women drink much less than men also – one study indicated that a group of women consumed about 14,000 drinks to induce cirrhosis, whilst men required more than 44,000 to achieve the same effect. Ethanol distributes in total body water only, so in women their greater fat content means that blood ethanol levels are higher than men of similar weight and age.

September 15, 2016 Posted by | books, genetics, medicine, Pharmacology | Leave a comment

Diabetes and the Metabolic Syndrome in Mental Health (II)

Here’s my first post about the book. This will be my last post about the book. In the coverage below I’ll include some quotes from the second half of the publication, as well as some comments.

“To date, no prospective study has directly compared the efficacy and tolerability of selective serotonin reuptake inhibitors (SSRIs), serotonin/ norepinephrine reuptake inhibitors (SNRIs), or other second-generation antidepressants in patients with diabetes versus patients without diabetes.”

“Weight is a common and well-known adverse effect of short-term and long-term treatment with TCAs, primarily as a result of excessive appetite. […] weight gain is the most common cause for premature discontinuation of all TCAs. […] TCAs are […] likely to impair diabetes control, because they increase serum glucose levels by up to 150%, increase appetite (particularly carbohydrate craving), and reduce the metabolic rate. […] SSRIs have been associated with both weight gain and weight loss. […] Weight gain is less likely with SSRIs when they are used short term — for 6 months or less. Contradictory evidence exists about whether an increase in body weight occurs in patients using SSRIs for 1 year or longer. […] The mean incidence of weight gain across comparative randomized controlled trials ranges from 4.1% for fluoxetine, 7.6% for sertraline, and 9.6% for paroxetine. […] SSRIs may reduce serum glucose by up to 30% and cause appetite suppression, resulting in weight loss. Fluoxetine should be used cautiously in patients with diabetes, because of its increased potential for hypoglycemia […]. Its side effects of tremor, nausea, sweating, and anxiety may also be misinterpreted as due to hypoglycemia.”

“Prior to the development of the second-generation antipsychotics (SGAs), or atypical antipsychotics, phenothiazines were the dominant therapy for schizophrenia. Numerous studies at this time began documenting that the use of phenothiazines led to aggravation of preexisting diabetes and the development of new-onset type 2 diabetes. […] high-potency neuroleptics […] appeared to be less implicated in the development of diabetes. These drugs eventually became the predominant form of therapy for schizophrenia […] Unfortunately, the high-potency neuroleptics are also associated with a high rate of occurrence of extrapyramidal symptoms, tardive dyskinesia, and subsequent noncompliance […]  In the late 1980s, a new class of antipsychotics, the thiobenzodiazepines or “atypical antipsychotics,” was introduced. […] One major advantage of these agents was a marked reduction in the occurrence of extrapyramidal symptoms. […] However, the atypical antipsychotics have also proven to carry their own unique side-effect profile. Side effects include substantial weight gain […] lipid abnormalities […] Hyperglycemia and diabetes are strongly associated with some of the newer atypical antipsychotics […] Thus, many psychiatrists are finding themselves in the difficult position of trading efficacy in the treatment of schizophrenia for an array of adverse metabolic side effects.”

“Weight gain is one of the more noticeable effects of all of the psychotropics. Although the SGAs appear to be a major culprit, TCAs, lithium, and mood stabilizers such as valproic acid or divalproex sodium and carbamazepine are also associated with weight gain. […] A range of evidence suggests that treatment with certain antipsychotic medications is associated with an increased risk of insulin resistance, hyperglycemia, and type 2 diabetes, compared with no treatment or treatment with alternative antipsychotics. […] A growing body of evidence supports the key observation that treatments producing the greatest increases in body weight and adiposity are also associated with a consistent pattern of clinically significant adverse effects on insulin resistance and changes in blood glucose and lipid levels. However, there are a growing number of cases of antipsychotic-associated hyperglycemia that involve patients without substantial weight gain, and reports that involve patients who improve when the offending agent is discontinued or who experience deterioration of glycemic control when re-challenged with the drug. […] Antipsychotics may lead to diabetes in susceptible individuals by causing decreased insulin secretion, increased insulin resistance, or a combination of both. Data suggest, however, that insulin resistance is primarily the responsible mechanism. […] The mechanism through which antipsychotics lead to insulin resistance is not clear.

“Many drugs may influence glucose insulin homeostasis. Commonly prescribed drugs that may have adverse effects on carbohydrate metabolism, especially in patients with diabetes mellitus or those at risk of developing glucose intolerance, include diuretics, beta-blockers, sympathomimetics, corticosteroids, and sex hormones”.

The book’s Table 4.11 include a really nice list of drugs, or drug classes, that can increase blood glucose levels, which includes quite a few commonly used drugs. A couple of to me surprising culprits on that list were marijuana and oral contraceptives; the oral contraceptives one certainly makes a lot of sense in retrospect (I don’t really know much about the metabolism of marijuana/cannabis, all I’ve ever learned about that stuff includes what was covered in the appendix of Coleman’s excellent textbook – and I have no personal experience…), I just hadn’t thought about the fact that very commonly used drugs like these may also have side effects of this nature).

“Patients with depression or bipolar depression may lack interest in their well-being and suffer from difficulty maintaining focus. Furthermore, many depressed patients suffer from decreased energy, psychomotor retardation, and changes in appetite, which may further promote weight gain. All of these make it very challenging to successfully implement a weight loss program in depressed patients. […] In addition, many patients with mental illnesses such as depression […] often state that eating is one of the few highlights of their day.” (So it’s probably a good idea to avoid giving these people drugs which will cause them to gain a substantial amount of weight/increase appetite/increase carbohydrate cravings, to the extent that this is possible…)

“Diabetes is considered a coronary artery disease equivalent by the National Cholesterol Education Panel (NCEP) […] Aspirin therapy is considered a routine part of secondary prevention in people with diabetes and a history of cardiovascular disease, and it is also recommended as part of primary prevention for cardiovascular disease in all patients with diabetes older than 40 years of age; additionally treatment with 75 to 325 mg/day of aspirin should be considered in patients 30 to 40 years of age with one additional cardiovascular risk factor.1,13 […] for all people older than 40 years of age with diabetes, statin therapy is recommended to lower the LDL by 30% to 40%, regardless of baseline levels.14 […] Lowering triglycerides to levels less than 150 mg/dL also confers cardiovascular benefit.1,14 However, hyperglycemia and hypertriglyceridemia are intricately linked, likely through elevations of free fatty acids. Free fatty acids are potent inhibitors of insulin action and transport, and act to disrupt glucose transport into skeletal muscle. Thus, triglyceride goals are often difficult to attain in uncontrolled diabetes.”

In some weird way some aspects of the last part of the book’s coverage was quite funny. So you have a diabetic whose disease has caused extensive damage to the nervous system leading to painful neuropathy. How do you treat the (in general difficult to treat) symptoms of neuropathy? Why, you give him tricyclic antidepressants (which will of course make his diabetes harder to treat, and cause him to gain weight). No, I’m not making this up:

“The most widely used medical treatments for symptoms of diabetic neuropathy include gabapentin and tricyclic antidepressants.”

Or how about this one – you have a type 2 diabetic who’s most likely overweight and who could probably benefit quite a bit from losing weight; why, let’s treat his diabetes with a drug that causes him to gain weight! People actually do this: “Thiazolidinediones (rosiglitazone, pioglitazone) act as agonists of the peroxisome proliferator-activator receptor gamma and improve insulin sensitivity at the tissue level. These agents are contraindicated in patients with heart failure and can worsen peripheral edema. Unfortunately, a common side effect of the glitazone class of agents is weight gain.” They’re not first-line agents, but they are used in diabetics. Just to make things even better, these drugs also seem to increase the risk of osteoporosis, a risk which is already somewhat elevated in type 2 diabetics: “Additionally, these drugs [thiazolidinediones] appear to decrease appendicular bone mass with associated increased risk of fractures.34

…or perhaps now some people might start thinking here: ‘Is stuff like this actually part of the explanation for Vestergaard’s findings described in the link above?’ I should add to these people that this is unlikely to be the case, especially considering the big difference between the (really quite substantial) type 1- and (significantly lower) type 2 fracture risk elevation; thiazolidinediones are not used in the treatment of type 1, and it’s not even a first-line treatment of type 2 – other explanations, such as those covered in Czernik & Fowlkes’s text, seem much more likely to matter (though in the context of a few individuals these drugs may still be of relevance).

“In addition to glycemic goals, nonglycemic treatment goals of blood pressure control, lipid management, and initiation of aspirin therapy are often necessary. For many patients, the diagnosis of diabetes results in multidrug therapy. For patients with mental illness who are likely to already be on multiple medications, the addition of several new agents can be difficult. Several studies have suggested that medication adherence in patients with psychiatric illness is poor at baseline,38 and may worsen when an increasing number of medications are prescribed.”

It’s also worth remembering here that “asymptomatic and chronic diseases needing long-term treatment […] result in poorer compliance”, although on the other hand “patient-controlled non-compliance [is] lower in treatment for diseases in which the relationship between non-compliance and recurrence is very clear, such as diabetes, compared to treatment for diseases in which this relationship is less clear” (Kermani and Davies). Combine psychiatric disease with chronic illnesses of a different kind and potential polypharmacy and non-compliance certainly becomes an issue worth taking into account when considering what might be the optimal treatment regime. It’s also worth keeping in mind that even in people without psychiatric problems adherence tends to be low in the case of antihypertensives and lipid-lowering drugs – again I refer to Kermani and Davies’ text:

“Chapman et al. (2005) recently examined compliance with concomitant antihypertensive and lipid-lowering drug therapy in 8406 enrollees in a US-managed care plan […] Less than half of patients (44.7 per cent) were adherent with both therapies three months after medication initiation, a figure that decreased to 35.8 per cent at 12 months.”

September 7, 2016 Posted by | books, diabetes, medicine | Leave a comment

Respirology

I was debating whether to blog this book at all, as it’s neither very long nor very good, but I decided it was worth adding a few observations from the book here. You can read my goodreads review of the publication here. Whenever quotes look a bit funny in the coverage below (i.e. when you see things like words in brackets or strangely located ‘[…]’, assume that the reason for this is that I tried to improve upon the occasionally frankly horrible language of some of the contributors to the publication. If you want to know exactly what they wrote, rather than what they presumably meant to write (basic grammar errors due to the authors having trouble with the English language are everywhere in this publication, and although I did choose to do so here I do feel a bit uncomfortable quoting a publication like this one verbatim on my blog), read the book.

I went off on a tangent towards the end of the post and I ended up adding some general remarks about medical cost, insurance and various other topics. So the post may have something of interest even to people who may not be highly interested in any of the stuff covered in the book itself.

“Despite intensive recommendations, [the] influenza vaccination rate in medical staff in Poland ranges from about 20 % in physicians to 10 % in nurses. […] It has been demonstrated that vaccination of health care workers against influenza significantly decreases mortality of elderly people remaining under [long-term care]. […] Vaccinating health care workers also substantially reduces sickness absenteeism, especially in emergency units […] Concerning physicians, vaccination avoidance stemmed from the lack of knowledge of protective value of vaccine (33 %), lack of time to get vaccinated (29 %), and Laziness (24 %). In nurses, these figures amounted to 55 %, 12 %, and 5 %, respectively (Zielonka et al. 2009).”

I just loved the fact that ‘laziness’ was included here as an explanatory variable, but on the other hand the fact that one-third of doctors cited lack of knowledge about the protective value of vaccination as a reason for not getting vaccinated is … well, let’s use the word ‘interesting’. But it gets even better:

“The questions asked and opinions expressed by physicians or nurses on vaccinations showed that their knowledge in this area was far from the current evidence-based medicine recommendations. Nurses, in particular, commonly presented opinions similar to those which can be found in anti-vaccination movements and forums […] The attitude of physicians toward influenza vaccination vary greatly. In many a ward, a majority of physicians were vaccinated (70–80 %). However, in the neurology and intensive care units the proportion of vaccinated physicians amounted only to 20 %. The reason for such a small yield […] was a critical opinion about the effectiveness and safety of vaccination. Similar differences, depending on medical specialty, were observed in Germany (4–71% of vaccines) (Roggendorf et al. 2011) […] It is difficult to explain the fear of influenza vaccination among the staff of intensive care units, since these are exactly the units where many patients with most severe cases of influenza are admitted and often die (Ayscue et al. 2014). In this group of health care workers, high efficiency of influenza vaccination has been clearly demonstrated […] In the present study a strong difference between the proportion of vaccinated physicians (55 %) and nurses (21 %) was demonstrated, which is in line with some data coming from other countries. In the US, 69 % of physicians and 46 % of nurses get a vaccine shot […] and in Germany the respective percentages are 39 % and 17 % […] In China, 21 % of nurses and only 13 % of physicians are vaccinated against influenza (Seale et al. 2010a), and in [South] Korea, 91 % and 68 % respectively (Lee et al. 2008).”

“[A] survey was conducted among Polish (243) and foreign (80) medical students at the Pomeranian Medical University in Szczecin, Poland. […] The survey results reveal that about 40 % of students were regular or occasional smoker[s]. […] 60 % of students declared themselves to be non-smokers, 20 % were occasional smokers, and 20 % were regular smokers”

40 % of medical students in a rather large sample turned out to be smokers. Wow. Yeah, I hadn’t seen that one coming. I’d probably expect a few alcoholics and I would probably not have been surprised about a hypothetical higher-than-average alcohol consumption in a sample like that (they don’t talk about alcohol so I don’t have data on this, I’m just saying I wouldn’t be surprised – after all I do know that doctors are high-risk for suicide), but such a large proportion smoking? That’s unexpected. It probably shouldn’t have been, considering that this is very much in line with the coverage included in Thirlaway & Upton’s book. I include some remarks about their coverage about smoking in my third post about the book here. The important observation of note from that part of the book’s coverage is probably that most smokers want to quit and yet very few manage to actually do it. “Although the majority of smokers want to stop smoking and predict that they will have stopped in twelve months, only 2–3 per cent actually stops permanently a year (Taylor et al. 2006).” If those future Polish doctors know that smoking is bad for them, but they assume that they can just ‘stop in time’ when ‘the time’ comes – well, some of those people are probably in for a nasty surprise (and they should have studied some more, so that they’d known this?).

A prospective study of middle-aged British men […] revealed that the self-assessment of health status was strongly associated with mortality. Men who reported poor health had an eight-fold increase in total mortality compared with those reporting excellent health. Those who assessed their health as poor were manual workers, cigarette smokers, and often heavy drinkers. Half of those with poor health suffered from chest pain on exertion and other chronic diseases. Thus, self-assessment of health status appears to be a good measure of current physical health and risk of death“.

It is estimated that globally 3.1 million people die each year due to chronic obstructive pulmonary disease (COPD). According to the World Health Organization (WHO 2014), the disease was the third leading cause of death worldwide in 2012. [In the next chapter of the book they state that: “COPD is currently the fourth leading cause of death among adult patients globally, and it is projected that it will be the third most common cause of death by 2020.” Whether it’s the third or fourth most common cause of death, it definitely kills a lot of people…] […] Approximately 40–50 % of lifelong smokers will go on to develop COPD […] the number of patients with a primary diagnosis of COPD […] constitutes […] 1.33 % of the total population of Poland. This result is consistent with that obtained during the Polish Spirometry Day in 2011 (Dabrowiecki et al. 2013) when 1.1 % of respondents declared having had a diagnosed COPD, while pulmonary function tests showed objectively the presence of obstruction in 12.3 % of patients.”

Based on numbers like these I feel tempted to conclude that the lungs may be yet another organ in which a substantial proportion of people of advanced age experience low-level organ dysfunction arguably not severe enough to lead to medical intervention. The kidneys are similar, as I also noted when I covered Longmore et al.‘s text.

“Generally, the costs of treatment of patients with COPD are highly variable […] estimates suggest […] that the costs of treatment of moderate stages of COPD may be 3–4-fold higher in comparison with the mild form of the disease, and in the severe form they reach up to 6–10 times the basic cost […] every second person with COPD is of working age […] Admission rates for COPD patients differ as much as 10-fold between European countries (European Lung White Book 2013).”

“In the EU, the costs of respiratory diseases are estimated at 6 % of the budget allocated to health care. Of this amount, 56 % is allocated for the treatment of COPD patients. […] Studies show that one per ten Poles over 30 year of age have COPD symptoms. Each year, around 4 % of all hospitalizations are due to COPD. […] One of the most important parameters regarding pharmacoeconomics is the hospitalization rate […] a high number of hospitalizations due to COPD exacerbations in Poland dramatically increase direct medical costs.”

I bolded the quote above because I knew this but had never seen it stated quite as clearly as it’s stated here, and I may be tempted to quote that one later on. Hospitalizations are often really expensive compared to drugs people who are not hospitalized take for their various health conditions, for example you can probably buy a year’s worth of anti-diabetic drugs, or more, for the costs of just one hospital admission due to drug mis-dosing. Before you get the idea that this might have ‘obvious implications’ for how ‘one’ should structure medical insurance arrangements in terms of copay structures etc., do however keep in mind that the picture here is really confusing:

3-3

Here’s the link, with more details – the key observation is that: “There is no consistency […] in the direction of change in costs resulting from changes in compliance”. That’s not diabetes, that’s ‘stuff in general’.

It would be neat if you could e.g. tell a story about how high costs of a drug always lead to non-compliance, which lead to increased hospitalization rates, which lead to higher costs than if the drugs had been subsidized. That would be a very strong case for subsidization. Or it would be neat if you could say that it doesn’t matter whether you subsidize a drug or not, because the costs of drugs are irrelevant in terms of usage patterns – people are told to take one pill every day by their doctor, and by golly that’s what they’re doing, regardless of what those pills cost. I know someone personally who wrote a PhD thesis about a drug where that clearly wasn’t the case, and the price elasticity was supposed to be ‘theoretically low’ in that case, so that one’s obviously out ‘in general’, but the point is that people have looked at this stuff, a lot. I’m assuming you might be able to spot a dynamic like this in some situations, and different dynamics in the case of other drugs. It gets even better when you include complicating phenomena like cost-switching; perhaps the guy/organization responsible for potentially subsidizing the drug is not the same guy(/-…) as the guy who’s supposed to pay for the medical admissions (this depends on the insurance structure/setup). But that’s not always the case, and the decision as to who pays for what is not necessarily a given; it may depend e.g. on health care provider preferences, and those preferences may themselves depend upon a lot of things unrelated to patient preferences or -incentives. A big question even in the relatively simple situation where the financial structure is – for these purposes at least – simple, is also the extent to which relevant costs are even measured, and/or how they’re measured (if a guy dies due to a binding budget constraint resulting in no treatment for a health condition that would have been treatable with a drug, is that outcome supposed to be ‘very cheap’ (he didn’t pay anything for  drugs, so there were no medical outlays) or very expensive (he could have worked for another two decades if he’d been treated, and those productivity losses need to be included in the calculation somehow; to focus solely on medical outlays is thus to miss the point)? An important analytical point here is that if you don’t explicitly make those deaths/productivity losses expensive, they are going to look very cheap, because the default option will always be to have them go unrecorded and untallied.

A problem not discussed in the coverage was incidentally the extent to which survey results pertaining to the cost of vaccination are worth much. You ask doctors why they didn’t get vaccinated, and they tell you it’s because it’s too expensive. Well, how many of them would you have expected to tell you they did not get vaccinated because the vaccines were too cheap? This is more about providing people with a perceived socially acceptable out than it is about finding stuff out about their actual reasons for behaving the way they do. If the price of vaccination does not vary across communities it’s difficult to estimate the price elasticity, true (if it does, you probably got an elasticity estimate right there), but using survey information to implicitly assess the extent to which the price is too high? Allow the vaccination price to vary next year/change it/etc. (or even simpler/cheaper, if those data exist; look at price variation which happened in the past and observe how the demand varied), and see if/how the doctors and nurses respond. That’s how you do this, you don’t ask people. Asking people is also actually sort of risky; I’m pretty sure a smart doctor could make an argument that if you want doctors to get vaccinated you should pay them for getting the shot – after all, getting vaccinated is unpleasant, and as mentioned there are positive externalities here in terms of improved patient outcomes, which might translate into specific patients not dying, which is probably a big deal, for those patients at least. The smart doctor wouldn’t necessarily be wrong; if the price of vaccination was ‘sufficiently low’, i.e. a ‘large’ negative number (‘if you get vaccinated, we give you $10.000’), I’m pretty sure coverage rates would go up a lot. That doesn’t make it a good idea. (Or a bad idea per se, for that matter – it depends upon the shape of the implicit social welfare function we’re playing around with. Though I must add – so that any smart doctors potentially reading along here don’t get any ideas – that a ‘large’ negative price of vaccination for health care workers is a bad idea if a cheaper option which achieves the same outcome is potentially available to the decision makers in question, which seems highly likely to me. For example vaccination rates of medical staff would also go up a lot if regular vaccinations were made an explicit condition of their employment, the refusal of which would lead to termination of their employment… There would be implicit costs of such a scheme, in terms of staff selection effects, but if you’re comparing solely those options and you’re the guy who makes the financial decisions..?)

August 22, 2016 Posted by | books, economics, medicine | Leave a comment

Diabetes and the Metabolic Syndrome in Mental Health (I)

As I stated in my goodreads review, ‘If you’re a schizophrenic and/or you have a strong interest in e.g. the metabolic effects of various anti-psychotics, the book is a must-read’. If that’s not true, it’s a different matter. One reason why I didn’t give the book a higher rating is that many of the numbers in there are quite dated, which is a bit annoying because it means you might feel somewhat uncertain about how valid the estimates included still are at this point.

As pointed out in my coverage of the human drug metabolism text there are a lot of things that can influence the way that drugs are metabolized, and this text includes some details about a specific topic which may help to illustrate what I meant by stating in that post that people ‘self-experimenting’ may be taking on risks they may not be aware of. Now, diabetics who need insulin injections are taking a drug with a narrow therapeutic index, meaning that even small deviations from the optimal dose may have serious repercussions. A lot of things influence what is actually the optimal dose in a specific setting; food (“food is like a drug to a person with diabetes”, as pointed out in Matthew Neal’s endocrinology text, which is yet another text I, alas, have yet to cover here), sleep patterns, exercise (sometimes there may be an impact even days after you’ve exercised), stress, etc. all play a role, and even well-educated diabetics may not know all the details.

A lot of drugs also affect glucose metabolism and insulin sensitivity, one of the best known drug types of this nature probably being the corticosteroids because of their widespread use in a variety of disorders, including autoimmune disorders which tend to be more common in autoimmune forms of diabetes (mainly type 1). However many other types of drugs can also influence blood glucose, and on the topic of antidepressants and antipsychotics we actually know some stuff about these things and about how various medications influence glucose levels; it’s not a big coincidence that people have looked at this, they’ve done that because it has become clear that “[m]any medications, in particular psychotropics, including antidepressants, antipsychotics, and mood stabilizers, are associated with elevations in blood pressure, weight gain, dyslipidemias, and/or impaired glucose homeostasis.” (p. 49). Which may translate into an increased risk of type 2 diabetes, and impaired glucose control in diabetics. Incidentally the authors of this text observes in the text that: “Our research group was among the first in the field to identify a possible link between the development of obesity, diabetes, and other metabolic derangements (e.g., lipid abnormalities) and the use of newer, second-generation antipsychotic medications.” Did the people who took these drugs before this research was done/completed know that their medications might increase their risk of developing diabetes? No, because the people prescribing it didn’t know, nor did the people who developed the drugs. Some probably still don’t know, including some of the medical people prescribing these medications. But the knowledge is out there now, and the effect size is in the case of some drugs argued to be large enough to be clinically relevant. In the context of a ‘self-experimentation’-angle the example is also interesting because the negative effect in question here is significantly delayed; type 2 diabetes takes time to develop, and this is an undesirable outcome which you’re not going to spot the way you might link a headache the next day to a specific drug you just started out with (another example of a delayed adverse event is incidentally cancer). You’re not going to spot dyslipidemia unless you keep track of your lipid levels on your own or e.g. develop xanthomas as a consequence of it, leading you to consult a physician. It helps a lot if you have proper research protocols and large n studies with sufficient power when you want to discover things like this, and when you want to determine whether an association like this is ‘just an association’ or if the link is actually causal (and then clarifying what we actually mean by that, and whether the causal link is also clinically relevant and/or for whom it might be clinically relevant). Presumably many people taking all kinds of medical drugs these days are taking on risks which might in a similar manner be ‘hidden from view’ as was the risk of diabetes in people taking second-generation antipsychotics in the near-past; over time epidemiological studies may pick up on some of these risks, but many will probably remain hidden from view on account of the amount of complexity involved. Even if a drug ‘works’ as intended in the context of the target variable in question, you can get into a lot of trouble if you only focus on the target variable (“if a drug has no side effects, then it is unlikely to work“). People working in drug development know this.

The book has a lot of blog-worthy stuff so I decided to include some quotes in the coverage below. The quotes are from the first half of the book, and this part of the coverage actually doesn’t talk much about the effects of drugs; it mainly deals with epidemiology and cost estimates. I thus decided to save the ‘drug coverage’ to a later post. It should perhaps be noted that some of the things I’d hoped to learn from Ru-Band Lu et al.’s book (blog coverage here) was actually included in this one, which was nice.

“Those with mental illness are at higher risk and are more likely to suffer the severe consequences of comorbid medical illness. Adherence to treatment is often more difficult, and other factors such as psychoneuroendocrine interactions may complicate already problematic treatments. Additionally, psychiatric medications themselves often have severe side effects and can interact with other medications, rendering treatment of the mental illness more complicated. Diabetes is one example of a comorbid medical illness that is seen at a higher rate in people with mental illness.”

“Depression rates have been studied and are increased in type 1 and type 2 diabetes. In a meta-analysis, Barnard et al. reviewed 14 trials in which patients with type 1 diabetes were surveyed for rates of depression.16 […] subjects with type 1 diabetes had a 12.0% rate of depression compared with a rate of 3.4% in those without diabetes. In noncontrolled trials, they found an even higher rate of depression in patients with type 1 diabetes (13.4%). However, despite these overall findings, in trials that were considered of an adequate design, and with a substantially rigorous depression screening method (i.e., use of structured clinical interview rather than patient reported surveys), the rates were not statistically significantly increased (odds ratio [OR] 2.36, 95% confidence interval [CI] 0.69–5.4) but had such substantial variation that it was not sufficient to draw a conclusion regarding type 1 diabetes. […] When it comes to rates of depression, type 2 diabetes has been studied more extensively than type 1 diabetes. Anderson et al. compiled a large metaanalysis, looking at 42 studies involving more than 21,000 subjects to assess rates of depression among patients with type 1 versus type 2 diabetes mellitus.18 Regardless of how depression was measured, type 1 diabetes was associated with lower rates of depression than type 2 diabetes. […] Depression was significantly increased in both type 1 and type 2 diabetes, with increased ORs for subjects with type 1 (OR = 2.9, 95% CI 1.6 –5.5, […] p=0.0003) and type 2 disease (OR = 2.9, 95% CI 2.3–3.7, […] p = 0.0001) compared with controls. Overall, with multiple factors controlled for, the risk of depression in people with diabetes was approximately twofold. In another large meta-analysis, Ali et al. looked at more than 51,000 subjects in ten different studies to assess rates of depression in type 2 diabetes mellitus. […] the OR for comorbid depression among the diabetic patients studied was higher for men than for women, indicating that although women with diabetes have an overall increased prevalence of depression (23.8 vs. 12.8%, p = 0.0001), men with diabetes have an increased risk of developing depression (men: OR = 1.9, 95% CI = 1.7–2.1 vs. women: OR = 1.3, 95% CI = 1.2–1.4). […] Research has shown that youths 12–17 years of age with type 1 diabetes had double the risk of depression compared with a teenage population without diabetes.21 This amounted to nearly 15% of children meeting the criteria for depression.

As many as two-thirds of patients with diabetes and major depression have been ill with depression for more than 2 years.44 […] Depression has been linked to decreased adherence to self-care regimens (exercise, diet, and cessation of smoking) in patients with diabetes, as well as to the use of diabetes control medications […] Patients with diabetes and depression are twice as likely to have three or more cardiac risk factors such as smoking, obesity, sedentary lifestyle, or A1c > 8.0% compared with patients with diabetes alone.47 […] The costs for individuals with both major depression and diabetes are 4.5 times greater than for those with diabetes alone.53

“A 2004 cross-sectional and longitudinal study of data from the Health and Retirement Study demonstrated that the cumulative risk of incident disability over an 8-year period was 21.3% for individuals with diabetes versus 9.3% for those without diabetes. This study examined a cohort of adults ranging in age from 51 to 61 years from 1992 through 2000.”

Although people with diabetes comprise just slightly more than 4% of the U.S. population,3 19% of every dollar spent on health care (including hospitalizations, outpatient and physician visits, ambulance services, nursing home care, home health care, hospice, and medication/glucose control agents) is incurred by individuals with diabetes” (As I noted in the margin, these are old numbers, and prevalence in particular is definitely higher today than it was when that chapter was written, so diabetics’ proportion of the total cost is likely even higher today than it was when that chapter was written. As observed multiple times previously on this blog, most of these costs are unrelated to the costs of insulin treatment and oral anti-diabetics like metformin, and indirect costs make out a quite substantial proportion of the total costs).

In 1997, only 8% of the population with a medical claim of diabetes was treated for diabetes alone. Other conditions influenced health care spending, with 13.8% of the population with one other condition, 11.2% with two comorbidities, and 67% with three or more related conditions.6 Patients with diabetes who suffer from comorbid conditions related to diabetes have a greater impact on health services compared with those patients who do not have comorbid conditions. […] Overall, comorbid conditions and complications are responsible for 75% of total medical expenditures for diabetes.” (Again, these are old numbers)

“Heart disease and stroke are the largest contributors to mortality for individuals with diabetes; these two conditions are responsible for 65% of deaths. Death rates from heart disease in adults with diabetes are two to four times higher than in adults without diabetes. […] Adults with diabetes are more than twice as likely to have multiple diagnoses related to macrovascular disease compared to patients without diabetes […] Although the prevalence of cardiovascular disease increases with age for both diabetics and nondiabetics, adults with diabetes have a significantly higher rate of disease. […] The management of macrovascular disease, such as heart attacks and strokes, represents the largest factor driving medical service use and related costs, accounting for 52% of costs to treat diabetes over a lifetime. The average costs of treating macrovascular disease are $24,330 of a total of $47,240 per person (in year 2000 dollars) over the course of a lifetime.17 Moreover, macrovascular disease is an important determinant of cost at an earlier time than other complications, accounting for 85% of the cumulative costs during the first 5 years following diagnosis and 77% over the initial decade. [Be careful here: This is completely driven by type 2 diabetics; a 10-year old newly diagnosed type 1 diabetic does not develop heart disease in the first decade of disease – type 1s are also at high risk of cardiovascular disease, but the time profile here is completely different] […] Cardiovascular disease in the presence of diabetes affects not only cost but also the allocation of health care resources. Average annual individual costs attributed to the treatment of diabetes with cardiovascular disease were $10,172. Almost 51% of costs were for inpatient hospitalizations, 28% were for outpatient care, and 21% were for pharmaceuticals and related supplies. In comparison, the average annual costs for adults with diabetes and without cardiovascular disease were $4,402 for management and treatment of diabetes. Only 31.2% of costs were for inpatient hospitalizations, 40.3% were for outpatient care, and 28.6% were for pharmaceuticals.16

Of individuals with diabetes, 2% to 3% develop a foot ulcer during any given year. The lifetime incidence rate of lower extremity ulcers is 15% in the diabetic population.20 […] The rate of amputation in individuals with diabetes is ten times higher than in those without diabetes.5 Diabetic lower-extremity ulcers are responsible for 92,000 amputations each year,21 accounting for more than 60% of all nontraumatic amputations.5 The 10-year cumulative incidence of lower-extremity amputation is 7% in adults older than 30 years of age who are diagnosed with diabetes.22 […] Following amputation, the 5-year survival rate is 27%.23 […] The majority of annual costs associated with treating diabetic peripheral neuropathy are associated with treatment of ulcers […] Overall, inpatient hospitalization is a major driver of cost, accounting for 77% of expenditures associated with individual episodes of lower-extremity ulcers.24

By 2003, diabetes accounted for 37% of individuals being treated for renal disease in the United States. […] Diabetes is the leading cause of kidney failure, accounting for 44% of all newly diagnosed cases. […] The amount of direct medical costs for ESRD attributed to diabetes is substantial. The total adjusted costs in a 24-month period were 76% higher among ESRD patients with diabetes compared with those without diabetes. […] Nearly one half of the costs of ESRD are due to diabetes.27” [How much did these numbers change since the book was written? I’m not sure, but these estimates do provide some sort of a starting point, which is why I decided to include the numbers even though I assume some of them may have changed since the publication of the book]

Every percentage point decrease in A1c levels reduces the risk of microvascular complications such as retinopathy, neuropathy, and nephropathy by 40%.5 However, the trend is for A1c to drift upward at an average of 0.15% per year, increasing the risk of complications and costs.17 […] A1c levels also affect the cost of specific complications associated with diabetes. Increasing levels affect overall cost and escalate more dramatically when comorbidities are present. A1c along with cardiovascular disease, hypertension, and depression are significant independent predictors of health care
costs in adults with diabetes.”

August 10, 2016 Posted by | books, diabetes, economics, medicine, Pharmacology | Leave a comment

Human Drug Metabolism (II)

My first post covering Coleman’s excellent book can be found here, and here you can read my goodreads review of the book; I think it makes sense to read those things before reading this post, if you have not already done that. As I believe I’ve previously mentioned (?) most non-fiction books I read, including those I do not blog, usually get a goodreads review, and actually I’m much more active on goodreads these days than I am on this blog. I have considered cross-posting goodreads reviews here on the blog, but I decided it might be best to just keep these things separate for the time being. I might change my mind about this, though; I don’t like how inactive the blog has become during the last few months, and goodreads reviews I’ve already written take almost no work to cross-post, so this would be an easy way to at least get some ‘activity’ here.

The book includes a lot of information that really pretty much everybody would be likely to benefit from knowing (how many people for example live their entire lives without consuming any alcohol, tobacco, or medical drugs? If you’ve ever consumed any of these things, the book has material of relevance included in the coverage…). I repeat myself here, but  some of the general observations included in the following seem to me to be important takeaways from the book: Drugs work (sometimes very) differently in different people, they interact with different things, including innocuous things like what you eat and drink and whether you exercise or not; drugs may interact with each other, in a very confusing variety of ways; some drugs are metabolized differently in people who have taken the drug for a while (‘induction’), compared to how the drug might be metabolized in someone who’s not taken the drug before (drug-naïve), and sometimes the ability to metabolize the drug faster/more efficiently may be lost (inhibition) because of a third factor, such as e.g. another drug or a dietary factor, which can be very dangerous (an improved ability to metabolize the drug because of habituation may also be lost due to non-consumption of the drug for some time, leading to a ‘reset’ of the metabolic pathway of relevance, an important factor in an abuse context where this can lead to overdose); there are huge racial and genetic differences in terms of how specific drugs are metabolized; the consequences of getting too much of a specific drug (toxicity) tend to be foreseeably different from the consequences of getting not enough of a drug (drug failure); efficient metabolism of a drug may depend upon the body’s ability not just to transform the xenobiotic compound into something useful, but also the ability to get rid of sometimes really quite toxic metabolites which might be created along the way as the body tries to get rid of that thing you just injected/ingested/etc. Many people don’t consider herbal remedies to be ‘real drugs’ and so neglect to tell their medical practitioner that they’re taking them/have recently stopped taking them, despite some of these having the potential to cause quite serious drug interactions (even if nothing is taken but herbal remedies; St. John’s Wort + kava kava = acute hepatitis? As noted in the book, “One point important to emphasize, is that assuming various herbal remedies do contain active and potent substituents, there is virtually nothing known clinically about what effects mixing herbal remedies might have, in terms of pharmacology and toxicity. This area is unfortunately left for patients to discover for themselves”).

This book is not ‘the whole story’ about drug metabolism and related stuff, it just scratches the surface, but the coverage serves to make it clear to you just how much stuff is to be found ‘below the surface’, and this is something I really like about the book. It makes you appreciate how little you know and how complex this stuff is. People write 500+ page textbooks like this one simply about CYP subtypes (I came across a different 1000+ page textbook also about a CYP subtype while reading the book so I know this one is hardly unique, but unfortunately I did not bookmark the book and I didn’t find the book after a brief search for it – but take my word for it, those books are out there…) and alcohol metabolism, they write 700 page textbooks about the side effects of psychiatric drugs (not the intended effects, that is – the side effects!) they write 800 page textbooks about aspirin and related drugs and about how drugs affect the liver… I know that in some circles it’s somewhat common for people to ‘experiment’ with various drugs and substances, illicit or otherwise; I also assume that most people who do this sort of thing have little idea what they’re actually doing and are likely taking a lot of risks the very existence of which they’re likely not aware of. Simply because there’s just so much stuff you need to know to even have a proper concept of what you’re doing when you’re dealing with how the human body works and how it responds to foreign substances we might choose to introduce into it. It might be that they wouldn’t care even if they knew because you’re probably rather low in risk aversion if you engage in that sort of experimentation in the first place (I incidentally am highly risk averse), but I do find it curious.

I have added some observations from the middle of the book below.

“Although there is growing awareness of the clinical problems posed by P-gp [P-glycoprotein] inhibition on drug bioavailability and toxicity, until recently it was very difficult to generalize and predict which classes of drug might be inhibitors of P-gp. […] There are dozens of drugs which are known inhibitors of P-gp […] it is often difficult to establish what contribution cellular transport systems make to bioavailability. Indeed, it is emerging that one of the reasons for the very wide variety of drug bioavailability in modern medicine could be the sheer number of possible inhibitors and substrates that exist for P-gp in the diet, such as a number of natural products like the flavonols, which can be as potent as cyclosporine or verapamil as P-gp inhibitors. Natural dietary inhibitors have advantages in their general lack of toxicity, but the basic problem of a lack of predictability in their effects on P-gp substrates remains. Since no two people’s diets are identical, the impact of P-gp modulation on drug absorption could be simply too complex to unravel.”

“the objectives of metabolizing systems could be summed up thus:
• To terminate the pharmacological effect of the molecule.
• Make the molecule so water-soluble that it cannot escape clearance, preferably by more than one route to absolutely guarantee its removal.
These objectives could be accomplished by:
• Changing the molecular shape so it no longer binds to its receptors.
• Changing the molecular lipophilicity to hydrophilicity to ensure high water solubility.
• Making the molecule larger and heavier, so it can be eliminated in bile as well as urine.
• Efflux pump systems, which ensure that a highly water-soluble metabolite actually leaves the cell to enter the bloodstream, before it is excreted in bile and urine. […]
CYP-mediated metabolism can increase hydrophilicity, but it does not always increase it enough and it certainly does not make the molecule any bigger and heavier, indeed, sometimes the molecule becomes lighter […] CYP-mediated metabolism does not always alter the pharmacological effects of the drug either […] However, CYPs do perform two essential tasks: the initial destabilization of the molecule, creating a ‘handle’ on it. […] CYPs also ‘unmask’ groups that could be more reactive for further metabolism. […] CYP-mediated preparation can make the molecule vulnerable to the attachment of a very water-soluble and plentiful agent to the drug or steroid, which accomplishes the objectives of metabolism. This is achieved through the attachment of a modified glucose molecule (glucuronidation), or a soluble salt such as a sulphate (sulphation) [see also this] to the prepared site. Both adducts usually make the drug into a stable, heavier and water-soluble ex-drug. […] with many drugs, their stability and lipophilicity mean that their clearance must take more than one metabolic operation to make them water-soluble.”

PXR [Pregnane X receptor], CAR [constitutive androstane receptor] and FXR [Farnesoid X receptor] are […] part of the process whereby the liver can sense whether its own metabolic capacity and physical size is sufficient to respond to homeostatic demands. Hence, alongside various growth factors, the NRs [nuclear receptors] facilitate the amazing process whereby the liver regenerates itself after areas of the organ are removed or damaged. […] As CYPs, UGTs [Glucuronosyltransferases], other biotransforming systems and efflux transporters are meeting the same xenobiotic or endobiotic stimuli in different tissues and degrees of exposure, it is logical that the […] receptor systems integrate and coordinate their responses. […] These multi-receptor mechanisms enable levels of induction to be customized for individual tissues to deal with different chemical threats. Essentially, according to diet, chemical and drug exposure, each individual will possess a unique expression array of UGTs and CYPs which will be constantly fine-tuned throughout life.”

“Sulphonation is accomplished by a set of enzyme systems known as sulphotransferases (SULTs) and they are found in most tissues to varying degrees of activity. […] The general aim of sulphonation is to make the substrate more water-soluble and usually less active pharmacologically. Sulphonated molecules are more readily eliminated in bile and urine. […] All SULTs are subject to genetic polymorphisms, with a high degree of individual variation in their expression and catalytic activities […] Regarding classification of the superfamily of SULTs, it is assumed that 47 per cent amino acid sequence homology is indicative of same family members and 60 per cent homology for subfamily members. To date, there are 47 mammalian SULT isoforms so far discovered, which are derived from ten human sulphotransferase gene families […] knowledge of the role of NRs and AhR [Aryl hydrocarbon receptor] in human SULT expression has progressed in animals but not really in humans. This is partly due to the fact that rodent SULT profiles are quite different to ours […] Many studies have been carried out in rodents, which have produced rather contradictory results […] It seems that whilst SULTs in general are not as responsive to inducers as CYPs and UGTs, their basal expression is much higher, although interindividual expression does vary considerably and this may have severe toxicological consequences, in terms of xenobiotic toxicity and carcinogenicity. There is also some evidence that diet is a strong influence on individual SULT profiles.”

“One of the main problems with the oxidation of various molecules by CYP enzymes is that they are often destabilized and sometimes form highly reactive products. […] CYPs occasionally form metabolites so reactive that they immediately destroy the enzyme by reacting with it, changing its structure and, therefore, its function. […] The most dangerous forms of reactive species are those that evade UGTs and SULT enzymes, or are inadvertently created by conjugation processes. These species escape into the cytosol and even into the nucleus, where potentially carcinogenic events may result. […] CYPs are not the only source of reactive species generated within cells. Around 75 per cent of our food intake is directed at maintaining our body temperature and a great deal of energy must be liberated from the food to accomplish this. Cells derive the vast majority of their energy through oxidative phosphorylation and this takes place in […] the mitochondria. […] In cells almost all the oxygen we breathe is consumed in oxidative phosphorylation, forming ATP, heat and reactive oxidant species in the mitochondria that could cause severe damage to the structure and function of the cell if they were allowed to escape. So all cells, particularly hepatocytes, have evolved a separate system to accommodate such reactive toxic products and this is based on a three amino acid (cysteine, glycine and glutamate) thiol known as glutathione, or GSH. Thiols in general are extremely effective at reducing and thus ‘quenching’ highly reactive, electrophilic species. […] if cells are depleted of GSH by blocking its synthesis (by using buthionine sulphoxime), cell death follows and the organism itself will die in a few days, due to uncontrolled activity of endogenous radicals. […] If GSH levels are not maintained in the cell over a long period of time, the cell wears out more quickly; for example, diabetic complications and HIV infection are linked with poor GSH maintenance.” [I did not know this…]

“There are several enzymes that promote and catalyze the reaction of GSH with potential toxins to ensure that reactive species are actively dealt with, rather than just passive GSH-mediated reduction. Probably the most important from the standpoint of drug metabolism are the GSH-S-transferases [‘GSTs’, which] are the key cellular defence against electrophilic agents formed from endogenous or xenobiotic oxidative metabolism. […] The GSTs are found in humans in several major classes. […] The classes contain several subfamilies […] These enzymes are polymorphic […] and their individual expression ranges from complete absence in some isoforms to overabundance as a response to anticancer therapy. […] The upregulation of GST is a serious problem within cancer therapeutics and resistance to a range of drugs including melphalan and doxorubicin is linked with GST detoxification. Much research has been directed at inhibitors of GST isoforms to reverse or even prevent the development of resistance to anti-neoplastic agents. Unfortunately this strategy has not been successful”

“once xenobiotics have been converted into low-toxicity, higher-molecular-weight and high-water-solubility metabolites by the combination of CYPs, UGTs, SULTs and GSTs, this appears at first sight to be ‘mission accomplished’. However, these conjugates must be transported against a concentration gradient out of the cell into the interstitial space between cells. Then they will enter the capillary system and thence to the main bloodstream and filtration by the kidneys. The biggest hurdle is the transport out of the cell, which is a tall order, as once a highly water-soluble entity has been created, it will effectively be ‘ion-trapped’ in the cell, as the cell membrane is highly lipophilic and is an effective barrier to the exit as well as entry of most hydrophilic molecules. […] failure to remove the hydrophilic products of conjugation reactions [from the cells] can lead to:
• toxicity of conjugates to various cell components;
• hydrolysis of conjugates back to the original reactive species;
• inhibition of conjugating enzymes.
If the cell can manage to transport them out, then they should be excreted in urine or bile and detoxification can proceed at a maximal rate. […] Consequently, an impressive array of multi-purpose membrane bound transport carrier systems has evolved which can actively remove hydrophilic metabolites and many other low molecular weight drugs and toxins from cells. The relatively recent […] term of Phase III metabolism has been applied to the study of this essential arm of the detoxification process. […] The main thrust of research into efflux transporters has been directed at the ABC-type transporters [this link actually has quite a bit of content, unlike some of the other wiki articles on these topics], of which there are 48 genes that code of a variety of ATP-powered pumps.”

“it is clear that the whole process of detection, metabolism and elimination of endobiotic and xenobiotic agents is minutely coordinated and is responsive to changes in load in individual tissues. The CYPs, UGTs, MRPs [Multidrug Resistance Proteins] and P-gp are all tightly regulated through the NR system of PXR, CAR, FXE, PPAR α, LXR etc, as well as the AhR receptor system [does it even make sense to keep adding links here? I’m not sure it does…]. Some enzyme/pump processes are closely linked, such as CYP3A4 and P-gp, as inducers powerfully increase both systems capacity. The reactive species protection ‘arm’ of biotransformation is also controlled through a separate but almost certainly ‘cross-talking’ Nrf2/Keap1 system which coordinates not only the interception of reactive species by GSTs, but also the supply of their GSH substrate, UGTs and the MRPs. This latter coordination is particularly relevant in resistance to cancer chemotherapy and happens because overexpression of any one entity alone cannot rid the cell of the toxin. […] The MRPs, GSH production and GST/UGT activity must be induced in concert. […] much of the integration and coordination of detoxification processes remains to be uncovered”.

Chapter 7, about ‘factors affecting drug metabolism’, has some very interesting stuff, but I think this post is quite long enough as it is. I might talk about that stuff in detail later on, but I make no promises.

August 9, 2016 Posted by | books, medicine, Pharmacology | Leave a comment

Human Drug Metabolism (I)

“It has been said that if a drug has no side effects, then it is unlikely to work. Drug therapy labours under the fundamental problem that usually every single cell in the body has to be treated just to exert a beneficial effect on a small group of cells, perhaps in one tissue. Although drug-targeting technology is improving rapidly, most of us who take an oral dose are still faced with the problem that the vast majority of our cells are being unnecessarily exposed to an agent that at best will have no effect, but at worst will exert many unwanted effects. Essentially, all drug treatment is really a compromise between positive and negative effects in the patient. […] This book is intended to provide a basic grounding in human drug metabolism, although it is useful if the reader has some knowledge of biochemistry, physiology and pharmacology from other sources. In addition, a qualitative understanding of chemistry can illuminate many facets of drug metabolism and toxicity. Although chemistry can be intimidating, I have tried to make the chemical aspects of drug metabolism as user-friendly as possible.”

I’m currently reading this book. To say that it is ‘useful if the reader has some knowledge’ of the topics mentioned is putting it mildly; I’d say it’s mandatory – my advice would be to stay far away from this book if you know nothing of pharmacology, biochem, and physiology. I know enough to follow most of the coverage, at least in terms of the big picture stuff, but some of the biochemistry details I frankly have been unable to follow; I think I could probably understand all of it if I were willing to look up all the words and concepts with which I’m unfamiliar, but I’m not willing to spend the time to do that. In this context it should also be mentioned that the book is very well written, in the sense that it is perfectly possible to read the book and follow the basic outline of what’s going on without necessarily understanding all details, so I don’t feel that the coverage in any way discourages me from reading the book the way I am – the significance of that hydrogen bond in the diagram will probably become apparent to you later, and even if it doesn’t you’ll probably manage.

In terms of general remarks about the book, a key point to be mentioned early on is also that the book is very dense and has a lot of interesting stuff. I find it hard at the moment to justify devoting time to blogging, but if that were not the case I’d probably feel tempted to cover this book in a lot of detail, with multiple posts delving into specific fascinating aspects of the coverage. Despite this being a book where I don’t really understand everything that’s going on all the time, I’m definitely at a five star rating at the moment, and I’ve read close to two-thirds of it at this point.

A few quotes:

“The process of drug development weeds out agents [or at least tries to weed out agents… – US] that have seriously negative actions and usually releases onto the market drugs that may have a profile of side effects, but these are relatively minor within a set concentration range where the drug’s pharmacological action is most effective. This range, or ‘therapeutic window’ is rather variable, but it will give some indication of the most ‘efficient’ drug concentration. This effectively means the most beneficial pharmacodynamic effects for the minimum side effects.”

If the dose is too low, you have a case of drug failure, where the drug doesn’t work. If the dose is too high, you experience toxicity. Both outcomes are problematic, but they manifest in different ways. Drug failure is usually a gradual process (days – “Therapeutic drug failure is usually a gradual process, where the time frame may be days before the problem is detected”), whereas toxicity may be of very rapid onset (hours).

“To some extent, every patient has a unique therapeutic window for each drug they take, as there is such huge variation in our pharmacodynamic drug sensitivities. This book is concerned with what systems influence how long a drug stays in our bodies. […] [The therapeutic index] has been defined as the ratio between the lethal or toxic dose and the effective dose that shows the normal range of pharmacological effect. In practice, a drug […] is listed as having a narrow TI if there is less than a twofold difference between the lethal and effective doses, or a twofold difference in the minimum toxic and minimum effective concentrations. Back in the 1960s, many drugs in common use had narrow TIs […] that could be toxic at relatively low levels. Over the last 30 years, the drug industry has aimed to replace this type of drug with agents with much higher TIs. […] However, there are many drugs […] which remain in use that have narrow or relatively narrow TIs”.

“metabolites are usually removed from the cell faster than the parent drug”

“The kidneys are mostly responsible for […] removal, known as elimination. The kidneys cannot filter large chemical entities like proteins, but they can remove the majority of smaller chemicals, depending on size, charge and water solubility. […] the kidney is a lipophilic (oil-loving) organ […] So the kidney is not efficient at eliminating lipophilic chemicals. One of the major roles of the liver is to use biotransforming enzymes to ensure that lipophilic agents are made water soluble enough to be cleared by the kidney. So the liver has an essential but indirect role in clearance, in that it must extract the drug from the circulation, biotransform (metabolize) it, then return the water-soluble product to the blood for the kidney to remove. The liver can also actively clear or physically remove its metabolic products from the circulation by excreting them in bile, where they travel through the gut to be eliminated in faeces.”

“Cell structures eventually settled around the format we see now, a largely aqueous cytoplasm bounded by a predominantly lipophilic protective membrane. Although the membrane does prevent entry and exit of many potential toxins, it is no barrier to other lipophilic molecules. If these molecules are highly lipophilic, they will passively diffuse into and become trapped in the membrane. If they are slightly less lipophilic, they will pass through it into the organism. So aside from ‘ housekeeping ’ enzyme systems, some enzymatic protection would have been needed against invading molecules from the immediate environment. […] the majority of living organisms including ourselves now possess some form of effective biotransformational enzyme capability which can detoxify and eliminate most hydrocarbons and related molecules. This capability has been effectively ‘stolen’ from bacteria over millions of years. The main biotransformational protection against aromatic hydrocarbons is a series of enzymes so named as they absorb UV light at 450 nm when reduced and bound to carbon monoxide. These specialized enzymes were termed cytochrome P450 monooxygenases or sometimes oxido-reductases. They are often referred to as ‘CYPs’ or ‘P450s’. […] All the CYPs accomplish their functions using the same basic mechanism, but each enzyme is adapted to dismantle particular groups of chemical structures. It is a testament to millions of years of ‘ research and development ’ in the evolution of CYPs, that perhaps 50,000 or more man-made chemical entities enter the environment for the first time every year and the vast majority can be oxidized by at least one form of CYP. […] To date, nearly 60 human CYPs have been identified […] It is likely that hundreds more CYP-mediated endogenous functions remain to be discovered. […] CYPs belong to a group of enzymes which all have similar core structures and modes of operation. […] Their importance to us is underlined by their key role in more than 75 per cent of all drug biotransformations.”

I would add a note here that a very large proportion of this book is, perhaps unsurprisingly in view of the above, about those CYPs; how they work, what exactly it is that they do, which different kinds there are and what roles they play in the metabolism of specific drugs and chemical compounds, variation in gene expression across individuals and across populations in the context of specific CYPs and how such variation may relate to differences in drug metabolism, etc.

“Drugs often parallel endogenous molecules in their oil solubility, although many are considerably more lipophilic than these molecules. Generally, drugs, and xenobiotic compounds, have to be fairly oil soluble or they would not be absorbed from the GI tract. Once absorbed these molecules could change both the structure and function of living systems and their oil solubility makes these molecules rather ‘elusive’, in the sense that they can enter and leave cells according to their concentration and are temporarily beyond the control of the living system. This problem is compounded by the difficulty encountered by living systems in the removal of lipophilic molecules. […] even after the kidney removes them from blood by filtering them, the lipophilicity of drugs, toxins and endogenous steroids means that as soon as they enter the collecting tubules, they can immediately return to the tissue of the tubules, as this is more oil-rich than the aqueous urine. So the majority of lipophilic molecules can be filtered dozens of times and only low levels are actually excreted. In addition, very high lipophilicity molecules like some insecticides and fire retardants might never leave adipose tissue at all […] This means that for lipophilic agents:
*the more lipophilic they are, the more these agents are trapped in membranes, affecting fluidity and causing disruption at high levels;
* if they are hormones, they can exert an irreversible effect on tissues that is outside normal physiological control;
*if they are toxic, they can potentially damage endogenous structures;
* if they are drugs, they are also free to cause any pharmacological effect for a considerable period of time.”

“A sculptor was once asked how he would go about sculpting an elephant from a block of stone. His response was ‘knock off all the bits that did not look like an elephant’. Similarly, drug-metabolizing CYPs have one main imperative, to make molecules more water-soluble. Every aspect of their structure and function, their position in the liver, their initial selection of substrate, binding, substrate orientation and catalytic cycling, is intended to accomplish this deceptively simple aim.”

“The use of therapeutic drugs is a constant battle to pharmacologically influence a system that is actively undermining the drugs’ effects by removing them as fast as possible. The processes of oxidative and conjugative metabolism, in concert with efflux pump systems, act to clear a variety of chemicals from the body into the urine or faeces, in the most rapid and efficient manner. The systems that manage these processes also sense and detect increases in certain lipophilic substances and this boosts the metabolic capability to respond to the increased load.”

“The aim of drug therapy is to provide a stable, predictable pharmacological effect that can be adjusted to the needs of the individual patient for as long is deemed clinically necessary. The physician may start drug therapy at a dosage that is decided on the basis of previous clinical experience and standard recommendations. At some point, the dosage might be increased if the desired effects were not forthcoming, or reduced if side effects are intolerable to the patient. This adjustment of dosage can be much easier in drugs that have a directly measurable response, such as a change in clotting time. However, in some drugs, this adjustment process can take longer to achieve than others, as the pharmacological effect, once attained, is gradually lost over a period of days. The dosage must be escalated to regain the original effect, sometimes several times, until the patient is stable on the dosage. In some cases, after some weeks of taking the drug, the initial pharmacological effect seen in the first few days now requires up to eight times the initial dosage to reproduce. It thus takes a significant period of time to create a stable pharmacological effect on a constant dose. In the same patients, if another drug is added to the regimen, it may not have any effect at all. In other patients, sudden withdrawal of perhaps only one drug in a regimen might lead to a gradual but serious intensification of the other drug’s side effects.”

“acceleration of drug metabolism as a response to the presence of certain drugs is known as ‘enzyme induction’ and drugs which cause it are often referred to as ‘inducers’ of drug metabolism. The process can be defined as: ‘An adaptive increase in the metabolizing capacity of a tissue’; this means that a drug or chemical is capable of inducing an increase in the transcription and translation of specific CYP isoforms, which are often (although not always) the most efficient metabolizers of that chemical. […] A new drug is generally regarded as an inducer if it produces a change in drug clearance which is equal to or greater than 40 per cent of an established potent inducer, usually taken as rifampicin. […] inducers are usually (but not always) lipophilic, contain aromatic groups and consequently, if they were not oxidized, they would be very persistent in living systems. CYP enzymes have evolved to oxidize this very type of agent; indeed, an elaborate and very effective system has also evolved to modulate the degree of CYP oxidation of these agents, so it is clear that living systems regard inducers as a particular threat among lipophilic agents in general. The process of induction is dynamic and closely controlled. The adaptive increase is constantly matched to the level of exposure to the drug, from very minor almost undetectable increases in CYP protein synthesis, all the way to a maximum enzyme synthesis that leads to the clearance of grammes of a chemical per day. Once exposure to the drug or toxin ceases, the adaptive increase in metabolizing capacity will subside gradually to the previous low level, usually within a time period of a few days. This varies according to the individual and the drug. […] it is clear there is almost limitless capacity for variation in terms of the basic pre-set responsiveness of the system as well as its susceptibility to different inducers and groups of inducers. Indeed, induction in different patients has been observed to differ by more than 20-fold.”

This one I added mostly because I didn’t know this and I thought it was worth including it here because it would make it easier for me to remember later (i.e., not because I figured other people might find this interesting):

CYP2E1 is very sensitive to diet, even becoming induced by high fat/low carbohydrate intakes. Surprisingly, starvation and diabetes also promote CYP2E1 functionality. Insulin levels fall during diet restriction, starvation and in diabetes and the formation of functional 2E1 is suppressed by insulin, so these conditions promote the increase of 2E1 metabolic capability. One of the consequences of diabetes and starvation is the major shift from glucose to fatty acid/tryglyceride oxidation, of which some of the by-products are small, hydrophilic and potentially toxic ‘ketone bodies’. These agents can cause a CNS intoxicating effect which is seen in diabetics who are very hypoglycaemic, they may appear ‘drunk’ and their breath will smell as if they had been drinking.”

A more general related point which may be of more interest to other people reading along here is that this is far from the only CYP which is sensitive to diet, and that diet-mediated effects may be very significant. I may go into this in more detail in a later post. Note that grapefruit is a major potentially problematic dietary component in many drug contexts:

“Although patients have been heroically consuming grapefruit juice for their health for decades, it took until the late 1980s before its effects on drug clearance were noted and several more years before it was realized that there could be a major problem with drug interactions […] The most noteworthy feature of the effect of grapefruit juice is its potency from a single ‘dose’ which coincides with a typical single breakfast intake of the juice, say around 200–300 ml. Studies with CYP3A substrates such as midazolam have shown that it can take up to three days before the effects wear off, which is consistent with the synthesis of new enzyme. […] there are a number of drugs that are subject to a very high gut wall component to their ‘first-pass’ metabolism […]; these include midazolam, terfenadine, lovastatin, simvastatin and astemizole. Their gut CYP clearance is so high that if the juice inhibits it, the concentration reaching the liver can increase six- or sevenfold. If the liver normally only extracts a relatively minor proportion of the parent agent, then plasma levels of such drugs increase dramatically towards toxicity […] the inhibitor effects of grapefruit juice in high first – pass drugs is particularly clinically relevant as it can occur after one exposure of the juice.”

It may sound funny, but there are two pages in this book about the effects of grapefruit juice, including a list of ‘Drugs that should not be taken with grapefruit juice’. Grapefruit is a well-known so-called mechanism-based inhibitor, and it may impact the metabolism of a lot of different drugs. It is far from the only known dietary component which may cause problems in a drug metabolism context – for example “cranberry juice has been known for some time as an inhibitor of warfarin metabolism”. On a general note the author remarks that: “There are hundreds of fruit preparations available that have been specifically marketed for their […] antioxidant capacities, such as purple grape, pomegranate, blueberry and acai juices. […] As they all contain large numbers of diverse phenolics and are pharmacologically active, they should be consumed with some caution during drug therapy.”

April 7, 2016 Posted by | biology, books, medicine, Pharmacology | Leave a comment

Eating disorders (II)

You can read my first post about the book, which lead to a brief comment exchange which may be of interest to people curious about diagnostics aspects, here. The book has a lot of stuff; in this post I’ll discuss the immune system, covered in chapter 5 of the book, as well as some ways that eating disorders may affect the skin (many of the remaining chapters of the book cover this topic). This will be my last post about the book.

In chapter 5 the authors start out by noting that adequate nutrition is an important factor in terms of maintaining immunocompetence and that malnutrition increases the risk of infection. Quite a few details are known about how specific aspects of nutritional deficiencies affect specific parts of the immune system. When both energy- and protein intake is insufficient (protein-energy malnutrition, PEM) this state of affairs is associated with atrophy of immune organs such as the thymus and spleen, as well as impairments in T cell populations (likely a natural consequence of thymus atrophy – the ‘T’ in ‘T cell’ stands for thymus…). Cytokine prodution (e.g. IL-1, IL-2, interferon-γ) is down-regulated in PEM, and the ability of T cells to respond appropriately to those cytokines is decreased. Impairments in macrophage phagocytotic function and neutrophils have been observed in malnourished individuals.

The authors note in the coverage that there now “seems to be consensus accepting that, overall, the manifestations of the immunocompromised status of ED patients are less frequent and severe than in PEM [3]. In general, the immune function seems to be better preserved than would be expected, considering the highly defective nutritional status of the patients. […] [some of] the most frequent findings described are leukopenia [white blood cell deficiency] with relative lymphocytosis [increased proportion of lymphocytes in the blood], [and] thrombocytopenia [platelet deficiency] […] immunocompetence and particularly T cell subsets are useful tools to follow-up the nutritional status in patients with ED. This asseveration applies also to BN patients, since T cell subsets seem to reflect their subclinical malnutrition, which is not evident from their weight status. […] Vomiting as a purging strategy is associated with a more deleterious effect on T cells […] Complement-system proteins […] have been found decreased in AN [anorexia nervosa] and BN [bulimia nervosa] [6,79] [and] seem to depend also on white adipose tissue mass. […] These proteins might be useful in the follow-up of AN patients, since C3 and C4 falls seem to occur when treated patients resume their restricting habits increasing their risk of relapse [81].”

Despite eating disorders having significant effects on the immune system, infection risk in people with eating disorders seems surprisingly to not be elevated, at least not until an advanced stage of the disease has been reached. There are multiple explanations offered for this observation, but the answer as to why this is is not completely clear. One reason might be that people with eating disorders tend to maintain relatively high protein and vitamin intake in a manner dissimilar from the intake patterns associated with classic starvation, mediating the effects of energy deficiency. Two other reasons offered both relate to the fact that the immune system does not respond normally to pathogens, and so to the extent that symptoms relate to immune responses to infection people with eating disorders have fewer symptoms; this relates to both down-regulation of memory T-cells and suppressed capacity to mount the classic acute-phase response to infection; a reduced febrile response to bacterial infection has been observed in anorexics. In the context of muted responses to infection, the hormone leptin (‘the satiety hormone’) may also be implicated; “there is a function for leptin as an up-regulator factor of inflammatory immune responses. Moreover, leptin production is acutely increased during infection and inflammation […] an impairment in this acute increase in leptin production in AN patients might be related to the lack of infection symptoms in these patients [26].” Interestingly leptin also seems to be downregulated in BN.

Okay, let’s move on and talk a little bit about how eating disorders may affect the skin. The book has a lot of stuff about this so this will not be an exhaustive review of the material covered in the book – but I did think I ought to talk a little bit about this stuff. Skin signs are important in a diagnostic context: “As most patients with eating disorders tend to minimize or even deny their disorder, the skin changes are sometimes the only indication that the patient has an eating disorder.” Some of the skin signs described in the book relate quite directly to specific behaviours (e.g. vomiting in purging subtypes), whereas others are of a more generalized nature and are rather due to the fact that the body does not get enough energy/micronutrients/etc. to handle all the tasks it’s supposed to handle. Some skin signs are considered ‘guiding signs’ of eating disorders, in the sense that they’re signs often found in an eating disorder context but are not usually found in the differential diagnoses natural to consider in the given clinical context, so they can be used as guiding tools in a diagnostic context. Examples of guiding signs include “lanugo-like body hair [very fine, soft, and usually unpigmented, downy hair] due to starvation, Russell’s sign [calluses on the knuckles or back of the hand] and [tooth] enamel erosions due to self-induced vomiting, and self-induced dermatoses due to psychiatric comorbidity.”

Frequent skin signs in eating disorders include dry, scaly skin; orange discolouration of the skin due to excessive consumption of beta carotene (carrots); the aforementioned lanugo-like body hair; coldness of the extremities (feet, toes) and bluish/purplish colouring of the hands and feet, caused by slow circulation (acrocyanosis); hair loss; inflammation of the lips and nail changes. “With a BMI between 17.5 and 16, the skin is usually pale or yellowish and cold, but no specific signs are found.” They note in the book that “Russell sign, dental enamel erosion, and salivary gland enlargement [elsewhere in the coverage they also dub this phenomenon ‘“chipmunk” cheeks of the bulimic’] are pathognomonic of purging behavior”. Dry skin is reported in 70% of people with anorexia nervosa (-AN), and acne is reported in 47–59% of patients – these are very common symptoms/consequences of AN. The same is the case for lanugo; in one study of AN patients (n=62), 77% had lanugo. In one study, alopecia was present in 67% of bulimics (n=122) and 61% of anorexics (n=62).

Observing the hands may be important: “Strumia [1], observing the hand of the patients with anorexia nervosa (AN), noticed that many peculiar skin signs, such as xerosis, acrocyanosis, carotenoderma, evident blood vessels due to decreased subcutaneous tissue, cold hand, nail dystrophy [“Brittle nails affect approximately 30% of patients with anorexia nervosa and bulimia nervosa”], Russell’s sign and artefacta, were located on the hands. Strumia used the term “anorectic’s hand” and suggested that, by examining the hand of a young patient, one can reasonably suspect an eating disorder. Only Russell’s sign is pathognomonic of eating disorders, but at least three signs, excluding Russell’s sign, are required for the diagnosis of “anorectic’s hand”, for example, xerosis, carotenoderma and cold hand. A perspicacious dermatologist should pay attention to this important sign when it appears in young females that show signs of reduced self-esteem and distorted perception of body weight.”

It is noted in the book that classical deficiency syndromes such as scurvy are very rare in AN because “AN is not commonly associated with vitamin deficiencies” – rather it’s the case that many anorectics over-supplement on vitamin supplements, which can paradoxically induce or worsen some skin complaints, such as e.g. xerosis (dry skin).

“the progression of anorexic pathology is accompanied by changing patterns in dietary habits [5]. These patterns include periods of low or no carbohydrate intake and an avoidance of dietary fats. They can also include patterns in which the primary foods consumed are fruits and vegetables. During this period, meat is often avoided. Changes in relative amounts of heavy to light isotopes [of nitrogen] in the hair indicate changes in the body’s metabolic state and dietary intake. […] By definition, individuals with anorexia or anorexia and bulimia are losing weight and do not get adequate nutrition. These individuals get their nitrogen largely from plants, and/or do not get sufficient nitrogen in their diet and are in nitrogen imbalance. By contrast, individuals diagnosed with only bulimia are maintaining their weight, and therefore get adequate nutrition and are likely not to be in nitrogen imbalance. […] Hatch et al. […] suggest that a distinction may be possible between anorexia and bulimia nervosa using 15N/14N and 13C/12C ratios in hair.”

“A reduced pain sensitivity has been found in eating disorder (ED) patients, but it is unclear what physiological and psychological factors are associated with this abnormality.”

January 26, 2016 Posted by | books, medicine | Leave a comment

Prioritization in medicine

This book is not exactly the first book I’ve read on these kinds of topics (see for example my previous coverage of related topics here, here, here, here, here, and here), but the book did have some new stuff and I decided in the end that it was worth blogging, despite the fact that I did not think the book was particularly great. The book is slightly different from previous books I’ve read on related topics because normative aspects are covered in much greater detail – as they put it in the preface:

“This volume addresses normative dimensions of methodological and theoretical approaches, international experiences concerning the normative framework and the process of priority setting as well as the legal basis behind priorities. It also examines specific criteria for prioritization and discusses economic evaluation. […] Prioritization is necessary and inevitable – not only for reasons of resource scarcity, which might become worse in the next few years. But especially in view of an optimization of the supply structures, prioritization is an essential issue that will contribute to the capability and stability of healthcare systems. Therefore, our volume may give useful impulses to face challenges of appropriate prioritization.”

I’m generally not particularly interested in normative questions, preferring instead to focus on the empirical side of things, but the book did have some data as well. In the post I’ll focus on topics I found interesting, and I have made no attempt here to make the coverage representative of the sort of topics actually covered in the book; this is (as usual) a somewhat biased account of the material covered.

The book observes early and often that there’s no way around prioritization in medicine; you can’t not prioritize, because “By giving priority to one group, you ration care to the second group.” Every time you spend a dollar on cancer treatment, well, that’s a dollar you can’t spend on heart disease. So the key question in this context is how best to prioritize, rather than whether you should do it. It is noted in the text that there is a wide consensus that approaching and handling health care allocation rules explicitly is preferable to implicit rationing, a point I believe was also made in Glied and Smith. A strong argument can be made that clear and well-defined decision-rules will lead to better outcomes than implicit allocation decisions made by doctors during their day-to-day workload. The risks of leaving allocation decisions to physicians involve overtaxing medical practitioners (they are implicitly required to repeatedly take decisions which may be emotionally very taxing), problematic and unfair distribution patters of care, and there’s also a risk that such practices may erode trust between patients and physicians.

A point related to the fact that any prioritization decision made within the medical sector, regardless of whether the decision is made implicitly or explicitly, will necessarily affect all patient populations by virtue of the fact that resources used for one purpose cannot be used for another purpose, is that the health care sector is not the only sector in the economy; when you spend money on medicine that’s also money you can’t be spending on housing or education: “The competition between health-related resources and other goods is generally left to a political process. The fact that a societal budget for meeting health needs is the result of such a political process means that in all societies, some method of resolving disagreements about priorities is needed.” Different countries have different approaches to how to resolve these disagreements (and in large countries in particular, lower-level regional differences may also be important in terms of realized care provision allocation decisions), and the book covers systems applied in multiple different countries, including England, Germany, Norway, Sweden, and the US state of Oregon.

Some observations and comments:

“A well-known unfairness objection against conventional cost-effectiveness analysis is the severity of diseases objection – the objection that the approach is blind as to whether the QALYs go to severely or to slightly ill patients. Another is the objection of disability discrimination – the objection that the approach is not blind between treating a life-threatening disease when it befalls a disabled patient and treating the same disease when it befalls a non-disabled patient. An ad hoc amendment for fairness problems like these is equity weighting. Equity weights are multiplication factors that are introduced in order to make some patient group’s QALYs count more than others.”

“There were an estimated 3 million people with diabetes in England in 2009; estimates suggest that the number of people with diabetes could rise to 4.6 million by 2030. There has also been a rapid rise in gastrointestinal diseases, particularly chronic liver disease where the under-65 mortality rate has increased 5-fold since 1970. Liver disease is strongly linked to the harmful use of alcohol and rising levels of obesity. […] the poorest members of the community are at most risk of neglecting their health. This group is more likely to eat, drink and smoke to excess and fail to take sufficient exercise.22 Accordingly, life expectancy in this community is shorter and the years spent of suffering from disability are much longer. […] Generic policies are effective in the sense that aggregate levels of health status improve and overall levels of morbidity and mortality fall. However, they are ineffective in reducing health inequalities; indeed, they may make them worse. The reason is that better-off groups respond more readily to public health campaigns. […] If policy-makers [on the other hand] disinvest from the majority to narrow the inequality gap with a minority resistant to change, this could reduce aggregate levels of health status in the community as a whole. [Health behaviours also incidentally tend to be quite resistant to change in general, and we really don’t know all that much about which sort of interventions work and/or how well they work – see also Thirlaway & Upton’s coverage] […] two out of three adults [in the UK] are overweight or obese; and inequalities in health remain widespread, with people in the poorest areas living on average 7 years fewer than those in the richest areas, and spending up to 17 more years living with poor health. […] the proportion of the total health budget invested in preventive medicine and health promotion […] is small. The UK spends about 3.6 % of its entire healthcare budget on public health projects of this nature (which is more than many other EU member states).”

Let’s talk a little bit about rationing. Rationing by delay (waiting lists) is a well-known method of limiting care, but it’s far from the only way to implicitly ration care in a manner which may be hidden from view; another way to limit care provision is to ration by dilution. This may happen when patients are seen on time (do recall that waiting lists are very common in the medical sector, for very natural reasons which I’ve discussed here on the blog before), but the quality of care that is provided to patients receiving care goes down. Rationing by dilution may sometimes be a result of attempts to limit rationing by delay; if you measure hospitals on whether or not they treat people within a given amount of time, the time dimension becomes very important in the treatment context and it may thus end up dominating other decision variables which should ideally take precedence over this variable in the specific clinical context. The book mentions as an example the Bristol Eye Hospital, where it is thought that 25 patients may have lost their sights because even though they were urgent cases which should have been high priority, they were not treated in time because there was a great institutional focus on not allowing waiting times of any patients on the waiting lists to cross the allowed maximum waiting time, meaning that much less urgent cases were treated instead of the urgent cases in order to make the numbers look good. A(n excessive?) focus on waiting lists may thus limit focus on patient needs, and similar problems pop up when other goals aside from patient needs are emphasized in an institutional context; hospital reorganisations undertaken in order to improve financial efficiency may also result in lower standards of care, and in the book multiple examples of this having happened in a British context are discussed. The chapter in question does not discuss this aspect, but it seems to me likely that rationing by dilution, or at least something quite similar to this, may also happen in the context of a rapid increase in capacity as a result of an attempt to address long waiting lists; if you for example decide to temporarily take on a lot of new and inexperienced nurses to lower the waiting list, these new nurses may not provide the same level of care as do the experienced nurses already present. A similar dynamic may probably be observed in a setting where the number of nurses does not change, but each patient is allocated less time with any given nurse than was previously the case.

“Public preferences have been shown not to align with QALY maximization (or health benefit maximization) across a variety of contexts […] and considerations affecting these preferences often extend well beyond strict utilitarian concerns […] age has been shown to be among the most frequently cited variables affecting the public’s prioritization decisions […] Most people are willing to use age as a criterion at least in some circumstances and at least in some ways. This is shown by empirical studies of public views on priority setting […] most studies suggest that a majority accepts that age can have some role in priority setting. […] Oliver [(2009)] found […] a wide range of context-dependent ‘decision rules’ emerged across the decision tasks that appeared to be dependent on the scenario presented. Respondents referenced reasons including maximizing QALYs,11 maximizing life-years or post-treatment quality of life,12 providing equal access to health care, maximizing health based on perceptions of adaptation, maximizing societal productivity (including familial roles, i.e. ‘productivity ageism’), minimizing suffering, minimizing costs, and distributing available resources equitably. As an illustration of its variability, he noted that 46 of the 50 respondents were inconsistent in their reasoning across the questions. Oliver commented that underlying values influence the respondents’ decisions, but if these values are context dependent, it becomes a challenge – if not impossible – to identify a preferred, overarching rule by which to distribute resources. […] Given the empirical observations that respondents do not seem to rely upon a consistent decision rule that is independent of the prioritization context, some have suggested that deliberative judgments be used to incorporate equity considerations […]. This means that decision makers may call upon a host of different ‘rules’ to set priorities depending on the context. When the patients are of similar ages, prioritization by severity may offer a morally justifiable solution, for example. In contrast, as the age discrepancy becomes greater between the two patients, there may be a point at which ‘the priority view’ (i.e. those who in the most dire conditions take precedence) no longer holds […] There is some evidence that indicates that public preferences do not support giving priority in instances where the intervention has a poor prognosis […] If older patients have poorer health outcomes as a result of certain interventions, [this] finding might imply that in these instances, they should receive lower priority or not be eligible for certain care. […] A substantial body of evidence indicates that the utilitarian approach of QALY maximization fails to adequately capture public preferences for a greater degree of equity into health-care distribution; however, how to go about incorporating these concerns remains unresolved.”

“roughly 35 % of the […] [UK] health expenditures were spent on the 13 % of our population over the age of 65. A similar statistic holds true for the European Union as well […] the elderly, on average, have many more health needs than the non-elderly. In the United States, 23 % of the elderly have five or more chronic health problems, some life-threatening, some quality-of-life diminishing (Thorpe et al. 2010). Despite this statistic, the majority of the elderly in any given year is quite healthy and makes minimal use of the health care system. Health needs tend to be concentrated. The sickest 5 % of the Medicare population consume 39 % of total Medicare expenditures, and the sickest 10 % consume 58 % of Medicare expenditures (Schoenman 2012). […] we are […] faced with the problem of where to draw the line with regard to a very large range of health deficiencies associated with advanced age. It used to be the case in the 1970s that neither dialysis nor kidney transplantation were offered as an option to patients in end-stage kidney failure who were beyond age 65 because it was believed they were not medically suitable. That is, both procedures were judged to be too burdensome for individuals who already had diminished health status. But some centers started dialyzing older patients with good results, and consequently, the fastest growing segment of the dialysis population today (2015) is over age 75. This phenomenon has now been generalized across many areas of surgery and medicine. […] What [many new] procedures have in common is that they are very expensive: $70,000 for coronary bypass surgery (though usually much more costly due to complication rates among the hyper-elderly); $200,000 for the LVAD [Left Ventricular Assist Device]; $100,000+ per month for prolonged mechanical ventilation. […] The average older recipient of an LVAD will gain one to two extra years of life […] there are now (2015) about 5.5 million Americans in various stages of heart failure and 550,000 new cases annually. Versions of the LVAD are still being improved, but the potential is that 200,000 of these devices could be implanted annually in the United States. That would add at least $40 billion per year to the cost of the Medicare program.”

“In the USA, around 40 % of premature mortality is attributed to behavioral patterns,2 and it is estimate[d] that around $1.3 trillion annually — around a third of the total health budget — is spent on preventable diseases.3 […] among the ten leading risk factors contributing to the burden of disease in high-income countries, seven can be directly attributed to unhealthy lifestyles. […] Private health insurance takes such factors into account when calculating premiums for health insurances (Olsen 2009). In contrast, publicly funded health-care systems are mainly based on the so-called solidarity principle, which generally excludes risk-based premiums. However, in some countries, several incentive schemes such as “fat taxes” […], bonuses, or reductions of premiums […] have recently been implemented in order to incorporate aspects of personal responsibility in public health-care systems. […] [An important point in this context is that] there are fundamental questions about whether […] better health leads to lower cost. Among other things, cost reductions are highly dependent on the period of time that one considers. What services are covered by a health system, and how its financing is managed, also matters. Regarding the relative lifetime cost of smokers, obese, and healthy people (never smokers, normal body mass index [BMI]) in the Netherlands, it has been suggested that the latter, and not the former two groups, are most costly — chiefly due to longer life and higher cost of care at the end of life.44 Other research suggests that incentivizing disease management programs rather than broader prevention programs is far more effective.45 Cost savings can therefore not be taken for granted but require consideration of the condition being incentivized, the organizational specifics of the health system, and, in particular, the time horizon over which possible savings are assessed. […] Policies seeking to promote personal responsibility for health can be structured in a very wide variety of ways, with a range of different consequences. In the best case, the stars are aligned and programs empower people’s health literacy and agency, reduce overall healthcare spending, alleviate resource allocation dilemmas, and lead to healthier and more productive workforces. But the devil is often in the detail: A focus on controlling or reducing cost can also lead to an inequitable distribution of benefits from incentive programs and penalize people for health risk factors that are beyond their control.”

January 21, 2016 Posted by | books, economics, medicine | Leave a comment

Oxford Handbook of Clinical Medicine (IV)

Here you can read my first three posts about the book. In this post I’ll talk a little bit about the book’s coverage of surgery; this is a major chapter with a lot of content.

In a surgical context prophylactic antibiotics are very often given to counter the risk of wound infection, especially in the gastrointestinal surgical context. The authors of the chapter don’t discuss the demerits of this approach at all, but I’ve read other people before who are critical of this way of doing things and before moving on to what the book has to say about related matters I thought I should remind you of some of the problems associated with the widespread prophylactic use of antibiotics in the surgical context – here’s part of what Gould and van der Meer had to say about this topic:

“Surgical prophylaxis is a common area of overuse [of antibiotics] as shown in many publications. Measured by total DDDs [defined daily doses], it can amount to around one third of a hospital’s total antibiotic use. This illustrates the potential for ecological damage although surgeons often ask whether 24 h or even single dose prophylaxis can really select for resistance. The simple answer is yes, but of course much of the problem is extension of prophylaxis beyond the perioperative period, often for several days in critical patients, perhaps until all lines and drains are removed. There is no evidence base in favour of such practices.” (link to further blog coverage of related topics here)

Omissions like these is incidentally one of several reasons why I did not give the Oxford handbook a higher rating than I did. With that out of the way let’s get back to the Oxford handbook coverage. They note in the surgery chapter that wound infection occurs in roughly one in five cases of elective GI surgery, and in up to 60 per cent of emergency surgery settings. Infections in surgical patients are not trivial events; they can lead to bleeding, wounds that reopen, and they can ultimately kill the patient. Another major risk associated with surgery in many different surgical contexts is the risk of deep vein thrombosis (-DVT). According to the book DVTs occur in 25-50% of surgical patients. That said, almost two-thirds of below-knee DVTs are asymptomatic and these rarely embolize to the lungs. Aside from surgery some other DVT risk factors worth knowing about include age (older patients are at higher risk), pregnancy, trauma, synthetic oestrogen (i.e., oral contraceptives), past DVT, cancer, obesity, and immobility.

As for DVTs in non-surgical contexts, I found it interesting that the book observes that “the evidence linking air travel to an increased risk of DVT is still largely circumstantial” – it also adds some additional data to contextualize the risk. For someone in the general population, the risk of DVT from a long-distance flight is estimated to be somewhere between one in 10.000 to one in 40.000, however for people in high-risk subgroups the incidence of DVT from flights lasting longer than 10 hours has been estimated at 4-6%. They argue in the book that travelers with multiple risk factors should consider compression stockings and/or a single prophylactic dose of low molecular-weight heparin for flights lasting longer than 6 hours; other ways to minimize risk include leg exercises, increased water intake and refraining from alcohol or caffeine during the flight. “There is no evidence to support the use of prophylactic aspirin.”

Even though I think a common impression is that surgeons always want to cut people open whereas internal medicine people will often think this is not necessary, ‘even surgeons’ are sometimes hesitant to cut you open. There are many reasons for this – the book covers a lot of surgical complications, but a perhaps particularly important long-term problem is this:
“Any surgical procedure that breaches the abdominal or pelvic cavities can predispose to the formation of adhesions [‘Adhesions are fibrous bands[1] that form between tissues and organs, often as a result of injury during surgery. They may be thought of as internal scar tissue that connects tissues not normally connected’], which are found in up to 90% of those with previous abdominal surgery; this is why we do not rush to operate on small bowel obstruction: the operation predisposes to yet more adhesions. Handling of the serosal surface of the bowel causes inflammation, which over weeks to years can lead to the formation of fibrous bands that tether the bowel to itself or adjacent structures […] Their main sequelae are intestinal obstruction (the cause in ~60% of cases […]) and chronic abdominal or pelvic pain.”

Appendicitis is a lot more common than I’d thought; lifetime incidence is 6%, with risk peaking during the second decade of life; according to the book it is the most common surgical emergency. A diagnosis of appendicitis is often wrong; in up to one in five patients a healthy appendix is removed. Another very common surgical procedure is surgical repair of an inguinal hernia; more than 100.000 of these surgeries are performed in the UK each year.

Though the book has a separate chapter specifically dealing with the topic of oncology (and palliative care), the surgical chapter of course also covers various cancers and their treatments. You’ll encounter the usual encouraging remarks about diseases with a ‘gloomy prognosis and non-specific presentation’, ‘[m]ost patients […] present with locally advanced (inoperable) or metastatic disease’ (both quotes are on the topic of carcinoma of the stomach); ‘[s]urvival rates are poor with or without treatment’ (carcinoma of the oesophagus); ‘rare, have an overall poor prognosis and are difficult to diagnose’ (bile duct and gallbladder cancers), ‘~80% present with inoperable disease’ (bile duct cancer). It’s sort of hard to find it encouraging that colorectal carcinoma, another cancer covered in that chapter, in general tend to have lower mortality than these others (“Overall 5yr survival is ~50%”) when you also keep in mind that it’s one of the most common cancers (it is the second most common cause of cancer deaths in the United Kingdom, and the third most common cancer), and so kill a lot more people overall (16.000 deaths/year). Another thing to note is that the survival rate of patients with metastatic disease in this context is still really terrible; the treated 5-year survival rate for patients with distant metastases is reported to be 6.6%, compared to e.g. a 48% survival rate in treated cases with ‘only’ regional lymph node involvement. They observe in their coverage that “[l]aparoscopic surgery has revolutionized surgery for colon cancer. It is as safe as open surgery and there is no difference in overall survival or disease recurrence.”

There are many bodily changes which take place in people as they age, and some of the potentially problematic changes only occasionally cause symptoms despite their presence in a large number of people. One example is gastrointestinal diverticula. These are outpouchings of the gut wall which are present in many people but do not always cause problems. According to the authors, diverticulosis is a term used to indicate that diverticula are present, whereas diverticular disease implies they the diverticula are symptomatic; the term diverticulitis is used when there’s inflammation of the diverticula. 30 % of people at the age of 60 living in the West are estimated to have diverticulosis, but the majority are asymptomatic – they are a common incidental finding when people have colonoscopies. Although they often do not cause problems they can cause perforation and hemorrhage (e.g. large rectal bleeds); the former complication has a high mortality, ~40%. Lack of dietary fiber is thought to be implicated in the pathophysiological processes leading to diverticulosis. Gallstones is another example of a common condition many people have without knowing it; gallstone prevalence is estimated at 8% at the age of 40. Risk is increasing in age and is higher in obese people. 90% remain asymptomatic. Smoking is known to increase the risk that gallstones become symptomatic. Renal stones are also common, with lifetime incidence estimated to be ‘up to’ (?) 15%. However males are three times as likely to get renal stones as are females, so in males in particular these things are very common. In the case of small stones (<5mm in lower ureter) ~90-95 % pass spontaneously on their own. The simplest and easiest way to lower risk of kidney stones is to drink plenty of fluids (but keep in mind that tea increases oxalate levels and thus may contribute to stone formation…). They note that calculi may be asymptomatic but do not provide estimates of how often this is the case; I assume one reason is that it’s really very difficult to get a good estimate of how often people pass stones they did not know they had – you mostly learn about these things when they cause trouble. Making a brief jump back to the topic of cancers it should perhaps be noted that although cancer is not usually thought of as a really not very worrisome asymptomatic condition, some forms of cancer actually sometimes may be just that; autopsy studies have indicated that 80% of men above the age of 80 have some form of prostate cancer.

Stress incontinence is leakage from an incompetent sphincter for example when intra-abdominal pressure rises, which it may do when people laugh or cough. It is very common in pregnancy and following birth, and it “occurs to some degree in ~50% of post-menopausal women”.

Although I didn’t think much of the epidemiology chapter, I did want to include a few observations from the chapter in this post:

“In one study looking at recommendations of meta-analyses where there was a later ‘definitive’ big trial, it turned out that meta-analyses got it wrong 30% of the time”.

“During the time it takes you to read this page, your better-connected patients may have checked out the latest recommendations of Guatemalan Guidelines on Gynaecomastia, or the NICE’S Treatise on Toxoplasmosis. Patients have time and motivation, whereas we have little time and our motivation may be flickering. This can seem threatening to the doctor who sees himself as a dispenser of wisdom and precious remedies. It is less threatening if we consider ourselves to be in partnership with our patients. The evidence is that those who use the internet to question their therapy receive a better service.” (A lot of related topics were incidentally covered in the Cochrane handbook The Knowledgeable Patient: Communication and Participation in Health – see this post for data on and discussion of these things).

 

January 18, 2016 Posted by | books, medicine | Leave a comment

Eating disorders… (I)

“Dermatologists have an important role in the early diagnosis of eating disorders since skin signs are, at times, the only easily detectable symptoms of hidden anorexia and bulimia nervosa. Forty cutaneous signs have been recognized”

The full title of the book is Eating Disorders and the Skin, but there’s a lot of stuff about eating disorders in general in this book as well, and I figured I’d mostly focus on the ‘general stuff’ in this post. Here’s my goodreads review of the book, which I gave 3 stars.

Here are the DSM-IV-TR diagnostic criteria for anorexia nervosa:

“1. Refusal to maintain body weight at or above a minimally normal weight for age and height (e.g., weight loss leading to maintenance of body weight less than 85% of that expected, or failure to make expected weight gain during period of growth, leading to body weight less than 85% of that expected).

2. Intense fear of gaining weight or becoming fat even though underweight.

3. Disturbance in the way in which one’s body weight or shape is experienced, undue influence of body weight or shape on self-evaluation, or denial of the seriousness of the current low body weight.

4.4. In postmenarcheal females, amenorrhea, i.e., the absence of at least three consecutive menstrual cycles.”

Interestingly, aside from anorexia [-AN] and bulimia [-BN] (diagnostic criteria here), there’s also a big category called ED-NOS – Eating Disorder Not Otherwise Specified. That’s for cases that don’t really fit into the standard criteria for specific eating disorders; they note than an example of this type could be a female fitting all diagnostic criteria for AN except that she has regular menses. It is perhaps worth mentioning here that surprisingly enough (…to me), menstrual irregularities are not limited to cases of AN, thus: “In almost 50% of bulimic patients, menstrual irregularities, such as oligomenorrhea or amenorrhea, take place”. They note in the book that there’s been some concern about the validity of the ED-NOS category, which makes up almost 60% of patients with an eating disorder. Eating disorders are much more common in females than in males (“Males are generally reported to account for 5–10% of anorectics and 10–15% of bulimics identified in the general population”), and particular subgroups mentioned to be at high risk are athletes, models and dancers. It’s noted in the book that most epidemiological studies are conducted in high-risk settings, whereas epidemiological studies assessing risk in the general population are somewhat rarer. One problem complicating matters a little in terms of estimating risk is that an eating disorder cannot be diagnosed through a self-report questionnaire; you need a structured or semi-structured interview to make a diagnosis, which makes things more expensive. As in other contexts one way to get around this issue, at least to some extent, is to employ multi-step screening protocols – in this case a two-step procedure in which individuals at high risk are identified at the first step through inexpensive means, and these individuals are then later assessed more carefully in the second step, employing more accurate (and expensive) methods.

They note that in Western countries, point prevalence of AN in female adolescent (the highest risk sub-group) is estimated at 0.2-1% of the population, whereas the prevalence studies on bulimia nervosa indicates that this eating disorder is somewhat more common, with the majority of studies finding prevalences of 1.5-5%; do recall again that most studies as already mentioned look at high-risk subgroups, so total population prevalence is likely to be lower than this. They observe in the book that general-practice studies find that the incidence of anorexia nervosa is less than one in ten-thousand per year (8 per 100,000 per year); so full-blown AN certainly is likely quite rare in low-risk populations.

On lifetime risk, the book notes that:

“Most of the epidemiological studies on ED [eating disorders] have evaluated the prevalence of full syndromes of both AN [anorexia nervosa] and BN [bulimia nervosa]. The few studies that have evaluated partial or subclinical manifestations of EDs in young females, however, found lifetime prevalence rates of 5–12% for atypical AN and 1–4.8% for atypical BN and up to 14.6% in adolescent samples”.

A review of epidemiological studies concluded that there’s no evidence of either a secular increase in AN or BN over time; to the extent that the number of people with diagnosed BN has increased over time, changes in diagnostic and referral practices likely account for this. On a related topic it is noted in the book that “It is a common idea among clinicians that early-onset cases of anorexia nervosa (AN) are increasing, but few data in the literature are available to demonstrate this trend.”

AN most commonly present among females at the age of 15-19, whereas BN presents a little later, most commonly at the age of 20-24. But eating disorders are not limited to teenagers and young adults: “Even if anorexia nervosa and bulimia nervosa occur characteristically in females during adolescence and young adulthood, there have been case reports of illness beginning after the age of 25 and even after the menopause, and some authors suggest that the rates of eating disorders in older patients may be increasing [2]. Clinical impression suggests that the late-onset cases present with more depressive features than the adolescent counterpart. […] dieting is considered one of the most salient precipitating factors.”

Self-report metrics can only help you so much when you’re trying to assess risk; a major problem in this context is that denial of illness is a very common feature in these patient populations (so you certainly can’t just ask people if their relationship with food/exercise etc. might be unhealthy…): “typically, [the] course [of an eating disorder] is characterized by a high fluidity between the diagnostic classes; furthermore, the patient often denies even to himself the psychiatric nature of the disease” (recall also that “denial of the seriousness of the current low body weight” is included in the diagnostic criteria). The book covers a lot of symptoms which relate to low body weight – like cold intolerance, bradycardia (slow heart rate), acrocyanosis (bluish discoloration of the hands and feet, caused by slow circulation), systemic hypotension (low blood pressure), lots of skin signs (I haven’t decided yet how much detail I’ll go into, so let’s leave it at that now) – or e.g. to purging behaviours (throat and tooth pain due to vomiting and enamel erosion), but it would go much too far to discuss all these in detail here. One to me interesting aspect of the coverage was that whereas BMI is a useful sign, it’s not itself a diagnostic criterion; the authors note that a BMI below 18.5 is considered pathological, but when listing main signs of anorexia nervosa the most important diagnostic sign (or at least the first one listed) is a BMI below 17.5; I assume part of the discussion surrounding the validity of the ED-NOS category probably relate to individuals who’re in this ‘border area’; they likely have some symptoms due to low body mass (like e.g. cold intolerance), but they don’t have full-blown AN (there are a lot of things that can go wrong when you have low body mass – there are a lot of symptoms described in this book!). It’s also important to note that very different symptom patterns can be present at similar levels of BMI, as the severity of symptoms also relate to how fast body mass decreases – the body is actually capable of adjusting quite well to lower energy intake states (in the short run at least), and so “if weight loss is gradual, it is possible to maintain, even for a long time, an apparent metabolic equilibrium.”

Anorexics have high mortality rates: “From a meta-analysis of 119 studies involving 5,590 patients, Steinhausen reported a crude mortality rate of 5% which exceeded 9% in a followup of 10 years.” Remember when thinking about those estimates that most of the people in these studies were likely young women – these numbers are high, and the authors note that anorexia nervosa “represents the major cause of death of young women in the age between 12 and 25 years.”

Most deaths are due to ventricular arrhythmia; the book goes into some detail about how anorexia affects the cardiovascular system, but I won’t discuss this in detail. An important observation is that: “Cardiac findings tend to disappear with weight recovery.” I assume this comment relates mostly to findings like QTc prolongation, QTc dispersion, and mitral valve prolapse, all of which are found in anorexics, whereas I’d be surprised if cardiac abnormalities related to direct damage to the heart muscle resolve themselves after weight gain, but the book does not go into details on this topic, except in the sense that it is noted that heart failure is uncommon in anorexics. Among those who survive their illness, osteoporosis is a major irreversible long-term problem. People with higher body mass tend to have a higher bone mineral density and thus a lower risk of osteoporosis (unless they get type 2 diabetes, in which case the situation is, well, complicated), so perhaps it’s not really surprising that women with AN and very low body mass index tend to develop osteoporosis. They certainly do:

“Osteopenia and osteoporosis represent one of the most relevant and potentially not reversible complications of eating disorders. This complication is particularly severe when eating disorders have an early onset […] Bone loss is an early effect of the disease, already present after 6–12 months […] In untreated patients, bone loss ranges from 4% up to 10% per year […]. In case of recovery, the progressive loss of BMD [bone mineral density] stops, but in most cases, a normal bone mass is not restored [64].”

It’s noted that bone loss is due to both hormonal and metabolic factors; estrogen plays a role, and “BMD loss in AN is more rapid and severe than in other hypoestrogenic conditions”. Despite this observation weight gain is considered the primary treatment modality of osteoporosis in this context (i.e., not estrogen therapy), and research using estrogen therapy to try to boost bone mineral density in anorexics who did not also gain weight has not been successful.

A to me interesting aspect of the coverage which I could not help but discuss here is how eating disorders relate to diabetes; the book has a few remarks on this topic:

“The concurrence of an eating disorder with insulin-dependent diabetes has been outlined by several researchers: especially bulimia nervosa and disorder not otherwise specified (EDNOS) are reported to be significantly higher in females with type 1 diabetes […] In case of comorbidity, ED onset followed the diagnosis of IDDM in 70% of the patients [10]. Specific aspects of diabetes and its management could, in fact, potentially increase a particular susceptibility to the development of an eating disorder: weight gain, associated with initiation of insulin treatment and dietary restraint, might, in fact, trigger body dissatisfaction and the drive for thinness with consequent weight control behaviors ranging from healthy to very unhealthy behaviors […] insulin omission [is] a common weight loss behavior in girls with IDDM and eating disorder […] APA Guidelines 2006 suggest that insulin omission should be considered a specific type of purging behavior in the next DSM revision”.

I don’t know if this suggested change has been implemented at this point, but it would make a lot of sense. To people who don’t know what this ‘insulin omission’ they talk about is all about, the short version is that if you’re a type 1 diabetic in need of regular insulin injections, if you don’t take enough insulin you lose weight and you can eat pretty much whatever you like without gaining weight; which is of course an unfortunate though likely very attractive option for young women to have. The downside of engaging in systematic insulin omission behaviour of that kind is that you’ll likely go blind from your diabetes and/or die of kidney failure or DKA if you do that for an extended period of time.

January 2, 2016 Posted by | books, diabetes, medicine, Psychology | 4 Comments