Whatever the case, the study authors pointed out that certain conditions -- such as insomnia, anxiety, high blood pressure and cardiac complications -- can be negatively affected by coffee drinking.
They further cautioned that the current findings need confirmation with continued research.
"This is quite an early finding," van Dam said. "And previous studies have been quite small. But the data we do have is very convincing in the sense that we feel comfortable that we definitely found no association between high coffee consumption and a higher stroke risk. So women can continue to enjoy their coffee and focus on other things to reduce stroke risk, such as engaging in more physical activity, reducing salt intake and stopping smoking."
Dr. Anthony Comerota, director of the Jobst Vascular Center at Toledo Hospital in Ohio, described the degree of benefit as "somewhat surprising."
"But what is not surprising," he said, "is the deleterious impact of cigarette smoking, which we know is the most potent risk factor -- perhaps other than diabetes -- for heart attack and stroke and general cardiovascular-related risk among both men and women."
Comerota suggested that future research should explore physical activity patterns among coffee drinkers and nondrinkers. "There may be behavior patterns which link increased physical activity with coffee drinking," he said, "and we know the more physical activity one has, the better cardiovascular risk reduction that person enjoys."
Another large study appearing in the same issue of Circulation offered insight into the impact of diet on stroke risk. It noted that American women who closely follow a traditional Mediterranean diet (high in monounsaturated fats, plant-based proteins, whole grains and fish) have a much lower risk for both heart disease and stroke.
As with van Dam's research, this study -- led by Teresa T. Fung of Simmons College and the Harvard School of Public Health in Boston -- was also based on analysis of participants in the Nurses' Health Study, nearly 75,000 of whom were tracked for two decades to see how their dietary habits stacked up against their incidence of both stroke and heart attack.
For more on diet and heart health, visit American Heart Association.
SOURCES: Rob M. van Dam, Ph.D., assistant professor, Harvard Medical School and Harvard School of Public Health, Boston; Anthony Comerota, M.D., director, Jobst Vascular Center, Toledo Hospital, Toledo, Ohio, and professor, surgery, University of Michigan, Ann Arbor, Mich.; March 3, 2009, Circulation