A few Cochrane reviews

Some reviews I had a look at after browsing the site:

i. Omega 3 fatty acids for prevention and treatment of cardiovascular disease (Review), by Hooper et al.

Main results Forty eight randomised controlled trials (36,913 participants) and 41 cohort analyses were included. Pooled trial results did not show a reduction in the risk of total mortality or combined cardiovascular events in those taking additional omega 3 fats (with significant statistical heterogeneity). Sensitivity analysis, retaining only studies at low risk of bias, reduced heterogeneity and again suggested no significant effect of omega 3 fats. […]

Authors’ conclusions It is not clear that dietary or supplemental omega 3 fats alter total mortality, combined cardiovascular events or cancers in people with, or at high risk of, cardiovascular disease or in the general population. There is no evidence we should advise people to stop taking rich sources of omega 3 fats, but further high quality trials are needed to confirm suggestions of a protective effect of omega 3 fats on cardiovascular health.”

(The review has 196 pages, so naturally there’s more stuff here if you’re interested…)

ii. Group behaviour therapy programmes for smoking cessation.

Main results

A total of 53 trials met inclusion criteria for one or more of the comparisons in the review. Thirteen trials compared a group programme with a self-help programme; there was an increase in cessation with the use of a group programme (N = 4375, relative risk (RR) 1.98, 95% confidence interval (CI) 1.60 to 2.46). There was statistical heterogeneity between trials in the comparison of group programmes with no intervention controls so we did not estimate a pooled effect. We failed to detect evidence that group therapy was more effective than a similar intensity of individual counselling. There was limited evidence that the addition of group therapy to other forms of treatment, such as advice from a health professional or nicotine replacement, produced extra benefit. There was variation in the extent to which those offered group therapy accepted the treatment. Programmes which included components for increasing cognitive and behavioural skills were not shown to be more effective than same length or shorter programmes without these components.

Authors’ conclusions

Group therapy is better for helping people stop smoking than self help, and other less intensive interventions. There is not enough evidence to evaluate whether groups are more effective, or cost-effective, than intensive individual counselling. There is not enough evidence to support the use of particular psychological components in a programme beyond the support and skills training normally included.”

iii. There is no convincing evidence that Ginkgo biloba is efficacious for dementia and cognitive impairment.

“36 trials were included but most were small and of duration less than three months. Nine trials were of six months duration (2016 patients). These longer trials were the more recent trials and generally were of adequate size, and conducted to a reasonable standard. Most trials tested the same standardised preparation of Ginkgo biloba, EGb 761, at different doses, which are classified as high or low.

The results from the more recent trials showed inconsistent results for cognition, activities of daily living, mood, depression and carer burden. Of the four most recent trials to report results three found no difference between Ginkgo biloba and placebo, and one reported very large treatment effects in favour of Ginkgo biloba. There are no significant differences between Ginkgo biloba and placebo in the proportion of participants experiencing adverse events. […]

Authors’ conclusions

Ginkgo biloba appears to be safe in use with no excess side effects compared with placebo. Many of the early trials used unsatisfactory methods, were small, and publication bias cannot be excluded. The evidence that Ginkgo biloba has predictable and clinically significant benefit for people with dementia or cognitive impairment is inconsistent and unreliable.”

iv. Antiplatelet agents and anticoagulants for hypertension.

Main results

Four trials with a combined total of 44,012 patients met the inclusion criteria and are included in this review. Acetylsalicylic acid (ASA) did not reduce stroke or ’all cardiovascular events’ compared to placebo in primary prevention patients with elevated blood pressure and no prior cardiovascular disease. In one large trial ASA taken for 5 years reduced myocardial infarction (ARR 0.5%, NNT 200), increased major haemorrhage (ARI 0.7%, NNT 154), and did not reduce all cause mortality or cardiovascular mortality. In one trial there was no significant difference between ASA and clopidogrel for the composite endpoint of stroke, myocardial infarction or vascular death.

In two small trials warfarin alone or in combination with ASA did not reduce stroke or coronary events.

The ATC meta-analysis of antiplatelet therapy for secondary prevention in patients with elevated blood pressure reported an absolute reduction in vascular events of 4.1% as compared to placebo. Data on the 10,600 patients with elevated blood pressure from the 29 individual trials included in the ATC meta-analysis was requested but could not be obtained.

Authors’ conclusions

Antiplatelet therapy with ASA for primary prevention in patients with elevated blood pressure provides a benefit, reduction in myocardial infarction, which is negated by a harm of similar magnitude, increase in major haemorrhage.

The benefit of antiplatelet therapy for secondary prevention in patients with elevated blood pressure is many times greater than the harm. […]

Further trials of antithrombotic therapy including with newer agents and complete documentation of all benefits and harms are required in patients with elevated blood pressure.”

May 30, 2013 - Posted by | medicine, papers

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