Exercise has long been associated with reduced risk of coronary heart
disease. However, the results of research into activity and risk of stroke
have been inconsistent. Now, 8 years of follow-up on thousands of women
indicates that the risk of all strokes and those caused by blockages of an
artery supplying the brain (ischemic) decreased significantly as the women's
activity levels increased.
Frank B. Hu, M.D., Ph.D., of the Harvard School
of Public Health in Boston, and colleagues studied a total of 72,488 female
nurses ages 40 to 65 who took part in the Nurses' Health Study. The nurses,
who did not have any diagnosed cardiovascular disease or cancer at baseline,
completed detailed physical activity questionnaires in 1986, 1988 and 1992.
Between 1986 and 1994, 407 new strokes occurred in this group. The authors
found that after controlling for age, body mass index (BMI), tobacco and
alcohol use, hypertension, and other factors, the risk of total stroke
decreased significantly with increasing physical activity. Walking was
associated with reduced risk of total stroke, according to the study
published in the June 14 issue of the Journal of the American Medical
Association. However, the researchers found that a brisk or striding walking
pace was associated with lower risk of ischemic stroke as well as total
stroke compared with average or casual pace walking.
Current guidelines from
the Centers for Disease Control and Prevention and the National Institutes
of Health recommend that Americans should accumulate at least 30 minutes of
moderate-intensity physical activity on most -- preferably all -- days of
the week. The authors add that the benefits of low- and moderate-intensity
activities (such as walking), compared with vigorous exercise, in the
prevention of cardiovascular disease remains controversial. Dr. Hu and
colleagues speculate that the protective effect of physical activity may be
partly mediated through its effect on various risk factors for stroke.
"Physical activity lowers blood pressure and increases high-density
lipoprotein (HDL) cholesterol (the 'good' cholesterol) concentration," the
authors say. The researchers also note that physical activity facilitates
weight loss and weight maintenance.
The study found that even women in the
study who were sedentary and didn't become active until later adulthood had
lower stroke risk than their counterparts who remained sedentary. "This
implies a relatively prompt effect of physical activity -- older adults can
enjoy the benefit of exercise even if they were sedentary for a long time,"
the researchers say. The study concludes that the findings lend further
support for current government guidelines that promote regular,
moderate-intensity physical activity for the prevention of chronic diseases.