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Critique 140: A meta-analysis shows that light alcohol consumption is associated with a reduced risk of stroke, while heavier drinking may increase risk – 5 June 2014

Most epidemiologic studies have shown a reduction in the risk of ischemic stroke (and total stroke, as ischemic stroke is by far the most common type in western countries) to be associated with light to moderate alcohol consumption. The present study, a meta-analysis, was based on 27 prospective studies; the authors categorized a reported intake of <15 g/day as light consumption, and 15-30 g/day as moderate consumption. The authors point out differences (greater smoking, larger amounts of alcohol) between Chinese subjects and those from other countries, which may explain some of the differences shown between alcohol’s effects in the different countries. They also point out that they had no data on the pattern of drinking (regular, moderate intake versus binge-drinking) or on the type of alcoholic beverage consumed.

The key results of the study are a significant 15% reduction in total stroke for low alcohol intake, no effect for moderate, and a 20% increased risk for heavy alcohol consumption (RR 1.20, 95% CI 1.01, 1.43). Analyses were also done according to type of stroke: for ischemic stroke and stroke mortality there were decreases for low alcohol intake, but no significant effects of either moderate or heavy intake. For hemorrhagic stroke, the RR for subjects reporting heavy alcohol intake was higher than that of abstainers, but none of the differences between drinkers and non-drinkers was statistically significant.

This meta-analysis supports previous findings of a decrease in the risk of most strokes with light drinking and possibly an increase in the risk for heavy drinking. Forum members generally agreed with the conclusions of the authors: “Low alcohol intake is associated with a reduced risk of stroke morbidity and mortality, whereas heavy alcohol intake is associated with an increased risk of total stroke. The association between alcohol intake and stroke morbidity and mortality is J-shaped. An alcohol intake of 0-20 grams/day is associated with decreased rates of stroke morbidity and mortality.”

Reference: Zhang C, Qin Y-Y,Chen Q, Jiang H, Chen X-Z, Xu C-L, Mao P-J, He J, Zhou Y-H. Alcohol intake and risk of stroke: A dose–response meta-analysis of prospective studies. Int J Cardiol 2014; pre-publication; http://dx.doi.org/10.1016/j.ijcard.2014.04.225.

For the full critique of this paper by members of the International Scientific Forum on Alcohol Research, please click here.
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