Physical Activity is Good for Stroke Prevention
ABSTRACTS & COMMENTARY
Sources: Sacco R, et al. Leisure-time physical activity and ischemic stroke risk. Stroke 1998;29:380-387; Kujala UM, et al. Relationship of leisure-time physical activity and mortality. JAMA 1998;279:440-444.
Regular exercise to produce physical fitness reduces premature mortality from cardiovascular disease. In light of this relationship, the Centers for Disease Control and Prevention1 and the NIH2 recommend moderately intense physical activity for at least 30 minutes daily if possible. In contrast, the relationship between physical activity and stroke has been less well established. The beneficial effects of exercise have been more apparent for men than women and for younger rather than older individuals.3 Therefore, Sacco and associates investigated the association between leisure-time physical activity and ischemic stroke in a multi-ethnic, elderly population in northern Manhattan. Case subjects had a first ischemic stroke, and control subjects were derived by random-digit dialing with 1:2 matching for age, sex, race, and ethnicity. A standardized questionnaire and in-person interview determined the frequency and duration of 14 recreational activities (light-moderate: walking, calisthenics, dancing, etc.; or heavy: hiking, tennis, swimming, etc.) over the prior two weeks. Over 2.5 years, 369 case subjects and 678 controls were enrolled. The mean age was 70 + 12 years; 57% were women, 18% were white, 30% black, and 52% Hispanic. Hypertension, diabetes, peripheral vascular disease, smoking, and cardiac disease were more common among the case subjects, while obesity was more common among the controls.
Engaging in any physical activity, whether light-moderate or heavy, was significantly protective for ischemic stroke after adjustment for risk factors for stroke, medical reasons for limited activity, education, and season of enrollment (odds ratio [OR] = 0.37; 95% confidence interval = 0.25-0.55). In contrast to pervious studies, the protective effect of physical activity was detected both in younger and older groups, in men and women, and in all racial and ethnic groups. There was a dose-response relationship for both intensity of physical activity (light-moderate OR = 0.39; heavy OR = 0.23) and duration (< 2 hours/week OR = 0.42; 2-5 hours/week OR = 0.31). The authors, therefore, advocate more emphasis on physical activity among the elderly in stroke prevention campaigns.
Kujala and colleagues sought to determine the relative importance in reducing premature mortality of factors over which an individual has no control, such as sex, early environment, and genetic susceptibility to disease, compared to factors that can be modified such as diet, smoking, and physical activity. The method they chose to distinguish between the effect of physical activity and family history of disease was to study twins.
In 1975, at baseline, the Finnish Twin Cohort comprised approximately 8000 healthy men and a like number of healthy women aged 25-64 years. Subjects completed a questionnaire that included items on physical activity, occupation, height, weight, alcohol use, smoking, and diseases. Those who reported exercising vigorously at least six times per month were classified as conditioning exercisers; other subjects were classified as either occasional exercisers or as sedentary.
All-cause mortality and discordant deaths among same-sex twin pairs were recorded from 1977 through 1994. Among the twin pairs who were healthy at baseline and discordant for death (n = 434), the odds ratio for death in occasional exercisers was 0.66 (95% CI = 0.46-0.94) and in conditioning exercisers was 0.44 (95% CI = 0.23-0.83) compared with those who were sedentary (P = 0.005). The beneficial effect of physical activity remained after controlling for other predictors of mortality. Therefore, leisure-time physical activity is associated with reduced mortality even after genetic and other familial factors are taken into account.
COMMENTARY
The study by Sacco et al detected a beneficial relationship between leisure-time physical activity and stroke. Benefits were observed for those younger and older than 65 years, both men and women, and among whites, blacks, and Hispanics. In this population of older individuals, walking was the most common form of recreational physical activity. The beneficial effects of even small amounts of leisure-time physical activity in the older population have not been reported previously and should be encouraging to older individuals who are unable to perform more vigorous exercises. Nevertheless, the dose-response relationship between level and duration of physical activity and protective effects from stroke should encourage those who can safely do so to increase their level of physical activity.
The twin cohort study from Finland emphasizes that physical fitness per se reduces mortality, despite the presence of predisposing familial and genetic factors.
The facts are in: Couch potatoes of all ages, arise and walk! Do more exercising than that if you can. -jjc
References
1. Pate RR, et al. JAMA 1995;273:402-407.
2. NIH Consensus Development Panel on Physical Activity and Cardiovascular Health. JAMA 1996;276:241-246.
3. Kiely DK, et al. The Framingham Study. Am J Epidemiol 1994;140:608-620.
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