Physical activity and risk of ischemic stroke in the Northern Manhattan study

BACKGROUND: It is controversial whether physical activity is protective against first stroke among older persons. We sought to examine whether physical activity, as measured by intensity of exercise and energy expended, is protective against ischemic stroke. METHODS: The Northern Manhattan Study is a prospective cohort study in older, urban-dwelling, multiethnic, stroke-free individuals. Baseline measures of leisure-time physical activity were collected via in-person questionnaires. Cox proportional hazards models were constructed to examine whether energy expended and intensity of physical activity were associated with the risk of incident ischemic stroke. RESULTS: Physical inactivity was present in 40.5% of the cohort. Over a median follow-up of 9.1 years, there were 238 incident ischemic strokes. Moderate-to heavy-intensity physical activity was associated with a lower risk of ischemic stroke (adjusted hazard ratio [HR] 0.65, 95% confidence interval [0.44-0.98]). Engaging in any physical activity vs none (adjusted HR 1.16, 95% CI 0.88-1.51) and energy expended in kcal/wk (adjusted HR per 500-unit increase 1.01, 95% CI 0.99-1.03) were not associated with ischemic stroke risk. There was an interaction of sex with intensity of physical activity (p = 0.04), such that moderate to heavy activity was protective against ischemic stroke in men (adjusted HR 0.37, 95% CI 0.18-0.78), but not in women (adjusted HR 0.92, 95% CI 0.57-1.50). CONCLUSIONS: Moderate-to heavy-intensity physical activity, but not energy expended, is protective against risk of ischemic stroke independent of other stroke risk factors in men in our cohort. Engaging in moderate to heavy physical activities may be an important component of primary prevention strategies aimed at reducing stroke risk.