A new analysis of the long-running Nurses Health Study shows that there is no increased risk of stroke among women who drink coffee and that in fact, consumption of four or more cups a day actually appears to be protective - as long as women do not also smoke.
Among women who smoke, the effect of coffee appears to be neutral, neither raising nor lowering the risk of stroke.
Recent studies have suggested that coffee does not increase the risk of coronary heart disease and protects against type 2 diabetes.
In this study, researchers analyzed data from the Nurses' Health Study, a prospective cohort of 83 076 women who were free of stroke, coronary heart disease, diabetes, or cancer at baseline. Coffee consumption was assessed first in 1980 and then every 2 to 4 years thereafter, with follow-up over 24 years through 2004.
Over this period, 2280 strokes occurred among the women: 1224 ischemic strokes, 426 hemorrhagic strokes, and 630 strokes of undetermined cause.
After adjustment for factors including age, smoking status, body-mass index, physical activity, alcohol intake, menopausal status, hormone therapy, aspirin use, and dietary factors, they found no increase in the risk for stroke associated with increasing coffee intake, and evidence for a protective effect for intakes of 2 or more cups per day vs less than 1 cup per month.
After further adjustment for high blood pressure, hypercholesterolemia, and type 2 diabetes, the inverse association remained significant, the authors noted.
Because cigarette smoking is more common in coffee drinkers and a strong confounder of stroke risk, they stratified the data by smoking status. They found that the association was stronger among never or past smokers than among current smokers, suggesting that "the potential benefit of coffee consumption cannot counterbalance the detrimental effects smoking has on health," the authors write.
