Dose-response effects of physical activity intensity and duration on frailty phenotype, frailty index, and survival: representative evidence from a 10-year national cohort of chinese older adults.

Frailty syndrome, characterized by diminished physiological reserves and heightened vulnerability to adverse health outcomes, is a major concern in aging populations. Physical activity (PA) is a proven intervention for frailty syndrome prevention and treatment, but evidence on how different intensities, durations, and doses of PA affect frailty and survival in China populations remains limited. We analyzed data from the China Health and Retirement Longitudinal Study (CHARLS), a nationally representative cohort with 10-year follow-up (2011-2020). Frailty syndrome was assessed using Frailty Phenotype (FP) and Frailty Index (FI). PA was categorized by intensity (low, moderate, high) and duration (0, 1-149, 150-299, ≥ 300 min/week). Multivariable regression evaluated cross-sectional associations between PA and frailty, and Cox models assessed PA-mortality relationships. Among 2,231 FP and 2,330 FI participants, higher PA-across all intensities-was inversely associated with frailty severity. Low-intensity PA (LPA) showed the strongest association (FP: β = -0.66; FI: β = -0.024; both p < 0.001). A clear dose-response trend emerged: ≥ 150 min/week of total PA associated with reduced frailty scores, while ≥ 300 min/week produced the greatest benefits. Survival analysis confirmed that higher PA was linked to improved 10-year survival, even among frailty syndrome individuals. Among Chinese adults aged ≥ 60 years, higher levels of physical activity, particularly HPA and MPA, were associated with a more favorable frailty profile and a lower hazard of 10-year all-cause mortality. However, these observational findings do not establish causality and should be confirmed in further prospective and interventional studies.