To address concerns that coffee might actually raise the risk of stroke in women, Harvard Researcher Rob M. van Dam and his team looked at data from 83,000 women who participated in the Nurses' Health Study, over the years 1980-2004. All women were healthy at the onset of the study, but by the end, almost 2,300 strokes were reported. The study included questionnaires that addressed the women's coffee- and tea-drinking habits as well as how much soda they consumed.
The researchers found that for women who drank two to three cups of caffeinated coffee per day, their risk for developing stroke was 19% lower than in non-coffee drinkers.
Eighty-four percent of the women said they regularly drank caffeinated coffee, 50% drank decaffeinated coffee, and 74% drank tea.
The researchers found that for women who drank two to three cups of caffeinated coffee per day, their risk for developing stroke was 19% lower than in non-coffee drinkers; for those who drank four or more cups, the risk was 20% lower. Even women who weren't such devout drinkers, only consuming five to seven cups per week, still had a reduced risk of stroke, at about 12%.
However, when the researchers teased apart the effect of smoking on the women's health, the results were even more striking. Among women who never smoked or had quit smoking and drank four or more cups of coffee a day, their risk for stroke was a whopping 43% lower. But for women who drank the same amount of coffee but also smoked cigarettes, their risk for stroke was only 3% reduced.
Caffeinated tea and soda did now show the same pattern of results, making the researchers believe that it is not actually the caffeine in coffee that provides these benefits, but rather some other, as yet unidentified, compound.
Van Dam and his team caution that while the results of the study are good evidence that drinking coffee doesn't raise the risk of stroke, and may lower it, more research needs to be done to further flesh out the relationship between coffee and stroke. He points out that drinking coffee has also been shown to increase the likelihood of other health problems, such as anxiety, insomnia, heart problems, and high blood pressure, so the findings should be taken with some discretion. He urges women to continue enjoying their daily coffee, but also to pay attention to other activities, "such as engaging in more physical activity, reducing salt intake and stopping smoking."