Socioeconomic status and intrinsic capacity trajectories among middle-aged and older adults in China: mediating role of cognitive leisure activities

OBJECTIVES: This study aimed to examine the association between socioeconomic status (SES) and intrinsic capacity (IC) trajectories among Chinese adults aged ≥45 years and evaluate the mediating role of cognitive leisure activities (CLA) on this relationship. DESIGN: A cohort study. SETTING AND PARTICIPANTS: Data were obtained from the China Health and Retirement Longitudinal Study (CHARLS, 2011-2015). The analytic sample comprised 3,922 community-dwelling adults aged ≥45 years with complete data on SES, CLA, and five domains of IC. MEASUREMENTS: IC trajectories were identified utilizing group-based trajectory modeling (GBTM) across locomotion, vitality, psychology, cognition, and sensory domains. SES was evaluated utilizing education and household wealth, whereas CLA was quantified by activity frequency. Multinomial logistic regression was employed to investigate the associations among SES, CLA, and IC trajectories, whereas mediation analysis was performed to evaluate the indirect effects of CLA. RESULTS: Among the 3,922 participants, GBTM identified four distinct IC trajectories from 2011 to 2015: High-level stable (n = 2,620; 66.8%), moderate-level declining (n = 620; 15.8%), low-level improving (n = 476; 12.1%), and low-level declining (n = 206; 5.3%). After adjusting for covariates, higher SES was associated with lower odds of belonging to less favorable trajectories compared to the high-level stable group. The corresponding odds ratios (ORs) were 0.830 (95% confidence interval [CI]: 0.769-0.896), 0.943 (95% CI: 0.902-0.986), and 0.899 (95% CI: 0.855-0.945), respectively. Higher levels of CLA were similarly associated with reduced odds of these trajectories (ORs = 0.480, 0.696, and 0.631; all p < 0.001). Mediation analysis revealed a significant indirect effect of SES on IC through CLA (a × b = 0.004; 95% bootstrap CI: 0.003-0.007), whereas the direct effect remained significant (c' = 0.037, p < 0.01), indicating partial mediation. CONCLUSION: Higher SES correlated with more favorable IC trajectories among Chinese adults aged ≥45 years, with CLA partially mediating this association and highlighting the significance of behavioral engagement in mitigating socioeconomic disparities in healthy aging.