Given the worldwide prevalence of alcohol consumption, as well as the high cost of death and disability from stroke, a clear understanding of the relationship between drinking and stroke risk could have important clinical and public health implications. Reynolds and colleagues performed a meta-analysis to assess the relationship between stroke and moderate alcohol consumption.

The authors identified 19 cohort studies and 16 case-control studies conducted worldwide that documented the relative risks of quantified alcohol consumption compared with abstinence. They found a nonlinear association between alcohol consumption and relative risk of total stroke. Alcohol consumption of less than 12 g per day, or less than one drink per day, was significantly associated with a decreased relative risk of total stroke compared with persons who did not drink. Alcohol consumption of more than 60 g per day, or more than five drinks daily, was associated with an increased relative risk of total stroke.

Among persons with ischemic stroke, the association between alcohol and stroke was J-shaped, with lowest relative risk occurring in persons consuming less than one drink or one to two drinks daily, whereas in the case of hemorrhagic stroke, the relative risk rose linearly with increased alcohol consumption. These differences held regardless of gender, although in women the relative risk was somewhat lower in those who had less than one drink per day.

In summary, the authors found a reduced relative risk of total and ischemic stroke among patients who drank moderately, and an increased relative risk among heavy drinkers. The association between heavy drinking and stroke may be attributable to the effects of alcohol on blood pressure and its contribution to coagulation disorders, cardiomyopathy, atrial fibrillation, and reductions in cerebral blood flow. It is likely that these findings are generalizable to many populations.