Light-to-moderate alcohol consumption has been consistently associated with lower risk of heart disease, but data for stroke are less certain, especially among women.
A total of 83,578 female participants of the Nurses' Health Study who were free of diagnosed cardiovascular disease and cancer at baseline were followed-up from 1980 to 2006. Data on self-reported alcohol consumption were assessed at baseline and updated approximately every 4 years, whereas stroke and potential confounder data were updated at baseline and biennially. Strokes were classified according to the National Survey of Stroke criteria . The authors found that the risk of total stroke is significantly lower among light-to-moderate consumers of alcohol than among subjects reporting no alcohol intake. In comparison with non-drinkers, the estimated risk was 17-21% lower for women averaging up to 15 grams of alcohol per day (one drink/day by US definitions of approximately 14 grams of alcohol, or two UK units of 8g). For consumers of larger amounts of alcohol, the risk of stroke increased at levels of consumption above 38g.
Data on the pattern of drinking (regularly, binge, etc.) were not reported. Among these predominantly light drinkers, there were no differences between effects on the risk of the most common type of stroke, ischemic stroke (due to atherosclerotic obstruction of a artery or an embolic clot) or the less-common hemorrhagic stroke (bleeding into the brain).
The results, with full adjustment for other factors that may affect risk, suggest a "J-shaped" curve for total stroke, with reductions in risk for light-to-moderate drinking and possibly an increase with greater amounts. In this study, the point at which the risk of women having a stroke exceeding that of non-drinkers was about 38 grams of alcohol per day (about 3 typical "drinks"). The frequency of use of hormones, multivitamins, physical activity, high cholesterol, and family history of myocardial infarction were very similar across categories of alcohol intake, suggesting that the women who consumed varying amounts of alcohol were generally similar in these characteristics to non-drinkers. The findings of lower BMI, increased smoking, greater HDL-cholesterol ( good cholesterol), and lower risk of diabetes with increasing alcohol consumption were expected, and further suggest that the assessments of alcohol were reasonably accurate.
The study supports many previous reports from observational epidemiologic studies that have shown a reduction in risk of the ischemic type of stroke from moderate alcohol intake. Some, but not all previous studies, show an increase in hemorrhagic stroke for any amounts of alcohol, but that was not seen in this study, possibly because there were few heavy drinkers in this group of nurses.
Reference: Jimenez M, Chiuve SE, Glynn RJ, Stampfer MJ, Camargo Jr CA, Willett WC, Manson JE, Rexrode KM. Alcohol Consumption and Risk of Stroke in Women. Stroke 2012, pre-publication.