DALLAS, October 9 -- Take a brisk walk. Climb the stairs at work. Dance the polka. If you engage in these and other similar physical activities for one hour per day, you can cut your risk for stroke by nearly 50 percent, according to researchers in a report in this month's Stroke: Journal of the American Heart Association.
In the study of 11,130 Harvard University alumni, researchers found that people who expended 2,000 kilocalories each week -- the equivalent of a one-hour brisk walk, five days a week -- had a 46 percent lower risk of stroke than those who did little to no exercise. Meanwhile, those expending 1,000 kilocalories a week -- the equivalent of walking briskly 30 minutes a day, five days a week -- had about a 24 percent reduction in stroke risk.
"Not only did we find that physical activity is associated with reduced risk of stroke, but also we have some ideas as to how much and what type of activity might work best," says the study's lead author, I-Min Lee, M.D., Sc.D., of the Harvard School of Public Health. "This finding provides additional support for the surgeon general's report on physical activity, which calls for at least 30 minutes of moderate intensity physical activity a day, most days of the week. We found that doubling that effort showed an even greater reduction in stroke risk."
Lee says that physical activity can help reduce or eliminate other common stroke risk factors including high blood pressure, high levels of blood cholesterol, obesity and diabetes. She and her co-author, Ralph Paffenbarger, Jr., M.D., an internationally-known exercise authority and professor emeritus at Stanford University, determined that activity of at least moderate intensity had a beneficial effect on stroke risk. The researchers defined moderate intensity as 4.5 times greater than a person's normal resting metabolic rate, which is one kilocalorie per kilogram of body weight per hour. "Walking, stair-climbing and participating in moderately intense activities such as dancing, bicycling and gardening were shown to reduce the risk of stroke," says Lee. "Light activity such as bowling and general housekeeping activity did not have the same effect. "We know that physical activity can reduce blood pressure and help slow the development of clogged arteries, keep weight down, reduce a person's cholesterol levels and help reduce clotting of the blood."
Strokes, the leading cause of disability in the United States, occur when blood flow to the brain is blocked by a blood clot or when fat-filled plaque clogs the vessels leading to the brain. Although this study looked almost exclusively at whether a correlation existed between physical activity and stroke in white men, Lee says that the implications of the research are likely applicable to women and minorities. A previous study in northern Manhattan had shown similar findings in women and minorities.
The Harvard Alumni Health Study started in 1962 as researchers tracked the health of people who graduated from Harvard between 1916 and 1950. In the study, researchers assessed physical activity in 1977 and followed men from 1977 until 1990 for occurrence of strokes. The researchers controlled for risk factors such as smoking, alcohol consumption, height and weight, high blood pressure and diabetes and still found that physical activity by itself was associated with decreased risk of stroke.
Media advisory: Dr. Lee can be reached by phone at (617) 732-4965, by fax at (617) 731-3843 or (617) 734-1437 or by e-mail at i-min.lee@channing.harvard.edu.(Please do not publish number.)