The Dynamic Associations of Social and Intellectual Activity With Frailty Trajectory in Middle-Aged and Older Adults in China: Nationwide Longitudinal Study

BACKGROUND: Research on the effects of social and intellectual activities on frailty remains limited, particularly longitudinal studies examining how these activities influence the dynamic progression of frailty over time. We aimed to examine this association in a nationally longitudinal study. OBJECTIVE: This study aimed to investigate the relationship between social and intellectual and frailty trajectories in the middle-aged and older Chinese population. Specifically, it sought to identify distinct frailty trajectories and quantify the longitudinal protective effects of social and intellectual activities against adverse frailty progression, while exploring differential impacts across age, sex, and residence subgroups. METHODS: This study used data from the China Health and Retirement Longitudinal Study and group-based trajectory modeling identified frailty trajectories over seven years. Frailty was assessed using a 38-item frailty index. The frequency of social activities and intellectual activity were quantified separately. Multivariate ordinal logistic regression analyzed associations between activity frequencies and trajectory membership. RESULTS: Three different trajectories of frailty were identified in this study: "low progressive trajectories" (n=7208, 65.8%), "moderate progressive trajectories" (n=3061, 28.5%), and "high progressive trajectories" (n=609, 5.7%). Compared to nonparticipants, frequent social activity participation reduced the likelihood of transitioning to the "moderate progressive" trajectory (odds ratio [OR] 0.84, 95% CI 0.75-0.94; P=.004). Intellectual activity engagement lowered risks of both "moderate" (OR 0.77, 95% CI 0.63-0.94; P=.01) and "high progressive" trajectories (OR 0.63, 95% CI 0.40-0.99; P=.04). Subgroup analyses revealed differential effects by age, sex, and residence. CONCLUSIONS: This study confirms the existence of heterogeneous long-term frailty trajectories among middle-aged and older Chinese adults, social and intellectual activities significantly mitigate frailty progression in Chinese middle-aged and older adults. Regular participation in structured social and intellectual activities can effectively delay frailty development in this population.