Physical Activity Lowers Stroke Risk in Women

Researchers led by Frank Hu, M.D., Ph.D., at the Harvard School of Public Health in Boston found that increasing levels of physical activity are associated with a significant reduction in risk of total stroke and stroke subtypes in women. The study, funded by the National Institutes of Health (NIH), supports recommendations from the Centers for Disease Control and Prevention (CDC) and NIH that Americans get at least 30 minutes of moderate physical activity on most days of the week.

The current study followed 72,488 female nurses from the prospective cohort Nurses’ Health Study, which was established in 1976. Participants ranged in age from 40 to 65 years and were free of cardiovascular disease and cancer at baseline. The nurses completed physical activity questionnaires in 1986, 1988, and 1992 assessing the average amount of time they spent per week engaged in vigorous activities such as running, bicycling, aerobics, swimming, and racquet sports. Questionnaires also assessed time spent walking, which was defined as a moderate-intensity activity.

The researchers examined the incidence of stroke among the nurses from 1986 to 1994. Strokes were classified as hemorrhagic (caused by bleeding into the brain), ischemic (caused by restricted blood flow to the brain), or of undetermined type. During the 8 years of follow-up, there were 407 cases of stroke, of which 258 were ischemic and 109 hemorrhagic. After controlling for age, body mass index (BMI), hypertension, and other factors, the study showed that each 3.5 hour per week increase in moderate or vigorous physical activity was associated with a 19 percent reduction in total stroke and a 29 percent reduction in ischemic stroke.

The researchers next looked at the health benefits of vigorous activity versus walking. They found that both brisk walking and non-walking vigorous activities showed a similar reduction in risk for stroke. This is encouraging news since walking is one of the most popular and easily accessible forms of exercise for American women.

The researchers also found that sedentary women who became more active in later life had a considerably lower risk for stroke than women who remained sedentary. This indicates a relatively immediate effect of physical activity on stroke risk.

This is the first large study of its kind that focuses on women. “With large sample size and detailed and repeated measures of physical activity, our study provides strong evidence for a graded inverse relationship between physical activity levels and risk for stroke,” the authors concluded.

The study is reported in the June 14, 2000 issue of the Journal of the American Medical Association and can be found on the web at: http://jama.ama-assn.org. s