Monik Jimenez ScD, BWH Department of Medicine, examined data from 83,578 female participants in the Nurses’ Health Study. They looked at data of women who had no evidence of cardiovascular disease or cancer at baseline and followed them for up to 26 years. Participants provided information on diet, including self-reported alcohol consumption, lifestyle factors and stroke events.
There were 2,171 incidents of stroke: 1,206 were ischemic strokes, 363 hemorrhagic strokes, and 602 were of an unknown or probable type. An ischemic stroke occurs when blood flow to the brain is blocked. A hemorrhagic stroke occurs when a blood vessel bursts in the brain.
Approximately 30 percent of women reported that they never drank alcohol, 35 percent reported very low levels of consumption, 37 percent drank moderately, and only 11 percent of women reported drinking more than the equivalent of one mixed drink per day on average.
In the study, low consumption was considered less than 4.9 grams daily (less than ½ glass of wine per day). Moderate consumption was considered 5 to 14.9 grams daily (½ to 1 ½ glasses of wine, one serving of a mixed drink, or one beer).
After analyzing the data, the researchers saw that women who consumed low to moderate amounts of alcohol had a lower risk of total stroke compared to women who never drank. Higher levels of alcohol intake were not associated with reduced risk of stroke.
The researchers speculate on several scenarios that may explain alcohol’s ability to reduce stroke risk. Alcohol may have components to prevent blood clots and cholesterol from building up in the arteries, both of which can lead to stroke. Higher levels of alcohol intake may increase the risk of high blood pressure and atrial fibrillation which are risk factors for stroke.
The study’s findings support the public health message issued by AHA regarding alcohol consumption. AHA recommends that women and men who consume alcohol should do so in moderation. This means one drink per day for women and one to two drinks per day for men. The AHA defines one drink as: one 12-ounce beer, 4 ounces of wine, 1½ ounces of 80-proof spirits, or 1 ounce of 100-proof spirits. Also, in light of the study findings, AHA cautions that people who abstain from alcohol should not start drinking due to the dangers associated with it (e.g., alcoholism).
This research was supported by grants from the National Heart, Lung and Blood Institute of the National Institutes of Health.