Physical Activity Frequency and the Risk of Stroke: A Nationwide Cohort Study in Korea

BACKGROUND: The current guideline recommends moderate- to vigorous-intensity physical activity (PA) at least 40 min/day for 3 to 4 days/week. Although recent evidence has demonstrated that low-dose PA could reduce cardiovascular mortality, the relationship between low-dose PA and the risk of stroke remains uncertain. METHODS AND RESULTS: Using data from a nation-wide sample cohort in Korea, we examined 336 326 individuals who received a general health examination between 2009 and 2010. Level of PA was assessed using a questionnaire for weekly PA frequencies regarding 3 intensity categories: light, moderate, and vigorous. Moderate- to vigorous-intensity PA (MVPA) was classified into 4 frequency categories: none, 1 to 2, 3 to 4, or ≥5 times/week. Cox proportional hazard models were constructed to estimate the risk of stroke. During the average follow-up of 3.6 years, 2213 stroke cases occurred. MVPA was none in 50%, 1 to 2 times/week in 20%, 3 to 4 times/week in 13%, and ≥5 times/week in 18% of the cohort. Individuals with MVPA 1 to 2 times/week had a 16% reduced risk of stroke (adjusted hazard ratio, 0.84; 95% confidence interval, 0.73-0.96) compared with those with no MVPA. The population attributable fraction of no MVPA was 12%, which was the second most important risk factor for a stroke after hypertension. CONCLUSIONS: Even 1 to 2 times a week of MVPA might be beneficial to prevent a first-ever stroke in the general population, although a quantitative validation of the questionnaire is needed. From a public health perspective, we need to encourage inactive people to start exercising with more-achievable goals.