The joint association of sleep duration and physical activity with frailty among older adults: the first evidence from CHARLS

OBJECTIVES: This study aimed to investigate the independent and joint associations of sleep duration and physical activity (PA) with longitudinal frailty developmental trajectories among older adults in the China Health and Retirement Longitudinal Study (CHARLS). METHODS: We utilized five waves of longitudinal data (2011-2020) from the CHARLS cohort. Group-based trajectory modeling (GBTM) was employed to identify distinct dynamic frailty trajectories. Sleep duration was categorized as short (< 6 h/day), normal (6-8 h/day), and long (> 8 h/day). PA levels were classified into light-level PA (LPA, < 600 MET-minutes/week), moderate-level PA (MPA, 600-3000 MET-minutes/week), and vigorous-level PA (VPA, > 3000 MET-minutes/week) based on the International Physical Activity Questionnaire (IPAQ) recommendations. Multinomial logistic regression models were conducted to examine the independent and joint effects of sleep and PA on the identified frailty trajectories. RESULTS: From 2011 to 2020, the overall pooled prevalence of frailty was the lowest in the VPA group (20.42%) and the normal sleep duration group (19.85%) compared with all other subgroups (P < 0.001). Three distinct frailty trajectories were identified: low-level stable, medium-level increase, and high-level increase. In the fully adjusted model, MVPA, normal and long sleep durations significantly reduced the risk of transitioning into the medium-level and high-level increase trajectories compared to LPA and short sleep. In joint analyses, compared to the LPA with short sleep reference group, significantly lower odds of entering the high-level increase trajectory were observed in the LPA with normal sleep subgroup (OR = 0.203, 95% CI: 0.049-0.841) and MPA with normal or long sleep subgroups (normal: OR = 0.081, 95% CI: 0.021-0.312; long: OR = 0.074, 95% CI: 0.014-0.383). Notably, VPA consistently conferred substantial protection across all sleep categories (short: OR = 0.224, 95% CI: 0.064-0.788; normal: OR = 0.063, 95% CI: 0.018-0.221; long: OR = 0.131, 95% CI: 0.033-0.521). CONCLUSIONS: The findings of this study demonstrate that adequate sleep duration and PA are crucial independent and synergistic protective factors against rapid frailty progression. These findings highlight that concurrently targeting both behaviors is a vital clinical strategy to mitigate severe frailty and promote healthy aging.