Association between changes in physical functions and risk of stroke: a prospective cohort study

BACKGROUND: The association between changes in physical functions and stroke incidence remains uncertain. METHODS: A total of 7978 participants without stroke from the China Health and Retirement Longitudinal Study (CHARLS) were recruited in 2011-2012 and followed up until 2020. We assessed annual changes in physical functions from 2011 to 2015, including absolute grip strength, relative grip strength, walking speed, chair-rising time and standing balance. The Cox proportional hazards model was applied to assess the longitudinal associations between annual changes in physical functions and stroke. Restricted cubic spline analyses were used to explore the dose-response relationships. RESULTS: During 71 714 person-years of follow-up, 549 incident stroke cases were reported. For each 1-kg absolute grip strength increment, 0.1-unit relative grip strength increment, or 1-point standing balance test score increment, the hazard of stroke was reduced by 12% [hazard ratio (HR): 0.88; 95% confidence interval (CI): 0.84-0.93], 53% (HR: 0.47; 95% CI: 0.34-0.64), 55% (HR: 0.45; 95% CI: 0.30-0.67), respectively. We found a negative linear dose-response association of the annual change in absolute and relative grip strength with incident stroke, as well as a nonlinear association between the annual change in standing balance and incident stroke. However, neither the annual change in walking speed nor chair-rising time was related to the incident stroke. CONCLUSIONS: A greater improvement in absolute grip strength, relative grip strength or standing balance was suggested to be associated with a lower risk of stroke amongst middle-aged and older people. These objectively measured physical function changes are imperative for high-risk population classification and stroke prevention.