A Meta-analysis of Alcohol and Stroke

Source: Tufts University
March 28, 2003

A moderate intake of alcohol has been shown to help protect against cardiovascular disease, but its effect on stroke risk is not as clear. US researchers recently took a look at available data on the subject; their findings are published in JAMA.

Examination of stroke risk

Researchers from Tulane University conducted a meta-analysis of 35 studies (both case control and cohort design) in which the end points were total strokes, ischemic strokes, and hemorrhagic strokes. For purposes of comparison, exposure was categorized into quintiles of alcohol consumption that ranged from none to more than 60 grams daily. (By US standards, one drink supplies about 12 grams of alcohol.)

Effect of alcohol

Data analyses showed a J-shaped curve, with subjects at both ends of the intake range at increased risk for stroke. Compared with abstainers, those who consumed less than 12 gm/day (about 1 drink) were about 20% less likely to suffer from ischemic stroke (relative risk, or RR=0.80, 95% CI, 0.67-0.96). However, those who consumed more than 60 gm/day were at increased risk of both ischemic stroke (RR=1.69, 95% CI, 1.34-2.15) and hemorrhagic stroke (RR= 2.18, 95% CI, 1.48-3.20). Analyzed separately, case control and cohort studies yielded similar results.

The researchers considered the possibility that studies showing null results may be less likely to be published. To test for this type of publication bias, they constructed a funnel plot (log relative risks plotted against standard of error measurements) to compare the relationship of relative risk to sample size. A high correlation between the two would suggest publication bias, but this was not found to be the case.

Possible pathways

Moderate alcohol intake probably cuts ischemic stroke risk for the same reasons that it is associated with a reduced risk of cardiovascular disease - alcohol increases HDL cholesterol levels and decreases platelet aggregation, both factors that help preserve normal arterial function. On the other hand, high alcohol intake can contribute to hypertension and coagulation disorders, increasing the risk of hemorrhagic stroke.

Advice to patients

The authors point out that given the widespread use of alcohol in the general population and the fact that stroke is a leading cause of death and disability, the results of their analysis are 'both important and timely.' In spite of the apparent stroke-limiting effect of moderate alcohol consumption, the authors caution that an across-the-board recommendation to consume alcohol is not warranted, and that the use of alcohol is an issue best discussed between adults and their own healthcare providers.

Source

• Alcohol consumption and risk of stroke: a meta-analysis. K. Reynolds, L. Lewis, J. Nolen,  et al., JAMA, 2003, vol. 289, pp. 579--588

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