Joint association of lung function and physical activity with risk of incident stroke among the US and Chinese adults

BACKGROUND: Impaired pulmonary function and physical inactivity are established risk factors for cerebrovascular disease, yet their combined contribution to stroke risk has not been systematically evaluated across diverse populations. This study aimed to evaluate the joint association of peak expiratory flow (PEF) and physical activity (PA) with incident stroke risk in US and Chinese adults. METHODS: This prospective cohort study enrolled 10,620 stroke-free participants aged 50 years or older from the Health and Retirement Study (HRS, n = 6,700) and the China Health and Retirement Longitudinal Study (CHARLS, n = 3,920). Participants were categorized into four groups based on cohort-specific median PEF and self-reported PA. Multivariable Cox proportional hazards models estimated hazard ratio (HR) for incident stroke over a 7-year median follow-up. RESULTS: Among HRS participants (n = 6,700, mean age 66.0 ± 10.3 years) and CHARLS participants (n = 3,920, mean age 61.5 ± 7.8 years), 590 incident strokes were recorded. Compared to the low PEF/inactive group, those with both high PEF and regular PA exhibited the lowest stroke risk in both cohorts (HRS: HR, 0.56 [95% CI, 0.38-0.82]; CHARLS: HR, 0.62 [95% CI, 0.44-0.89]). Participants with only one favorable factor showed attenuated and inconsistent risk reductions. No significant interactions were found by age, sex, or comorbidities (all P for interaction > 0.05). CONCLUSIONS: Preserved pulmonary function combined with regular physical activity is associated with a significantly lower stroke risk across diverse populations. Integrated assessment of these factors may improve stroke risk stratification and inform targeted prevention strategies.