Boston University Medical Center researchers tracked 83,578 female participants of the Nurses' Health Study who were free of diagnosed cardiovascular disease and cancer at baseline. Follow-up occurred from 1980 to 2006.
Data on self-reported alcohol consumption were assessed at baseline and updated approximately every four years, but stroke and potential confounder data were updated at baseline and biennially.
Strokes were classified using National Survey of Stroke criteria.
The study, scheduled to be published in the journal Stroke, found the estimated risk was 17 percent to 21 percent lower for women averaging one drink, in comparison with non-drinkers, but consumers of larger amounts of alcohol -- about three typical drinks -- had a higher risk of stroke. Data on binge drinking were not reported.
Among 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 an artery or an embolic clot -- or the less-common hemorrhagic stroke, bleeding into the brain.
The frequency of use of hormones, multivitamins, physical activity, high cholesterol and family history of heart attack were very similar across categories of alcohol intake, suggesting women who consumed varying amounts of alcohol were generally similar in these characteristics to non-drinkers, the researchers said.