Temporal Dynamics of Frailty and Depression Among Chinese Older Adults: A Hierarchical Age-Period-Cohort Analysis

Background China faces unprecedented population aging, with projections indicating 395 million individuals aged ≥ 65 years by 2050. This study utilized longitudinal data from the China Health and Retirement Longitudinal Study (CHARLS) spanning 2011–2020 to examine temporal dynamics of frailty and depressive symptoms among Chinese older adults through age-period-cohort (APC) analysis. The research aimed to identify critical health determinants, elucidate impacts of social transitions and intergenerational differences on health trajectories, and provide empirical evidence for optimizing targeted interventions. Methods Grounded in life course theory and positive aging frameworks, this study employed advanced statistical methodologies including Hierarchical Age-Period-Cohort (HAPC) modeling, Latent Class Growth Analysis (LCGA), and cumulative risk function analysis. The analytic sample comprised 17,392 person-observations (baseline n = 4,037) of individuals aged ≥ 60 years. Frailty was assessed using the Frailty Index (FI), while depressive symptoms were measured by the CES-D-10 scale. HAPC models disentangled age-related physiological decline, period effects reflecting policy and environmental contexts, and cohort effects capturing intergenerational health disparities. LCGA identified heterogeneous trajectory classes, and cumulative risk analysis characterized temporal patterns of health deterioration across birth cohorts. Results Age effects demonstrated accelerating frailty trajectories with advancing age, particularly beyond age 75. Period effects revealed elevated frailty risk in 2013 with subsequent decline by 2018, while depressive symptomatology peaked in 2013 and 2020—the latter likely reflecting COVID-19 pandemic impacts. Cohort effects showed the 1941–1945 birth cohort exhibited significantly lower depressive risk, potentially attributable to enhanced psychological resilience cultivated through early-life adversity. LCGA identified three distinct trajectory classes for both frailty and depressive symptoms, revealing substantial population heterogeneity. Cumulative risk analysis demonstrated earlier-born cohorts manifested lower initial health risks, whereas later-born cohorts showed accelerated risk accumulation during extended follow-up. Conclusions Health trajectories among Chinese older adults reflect complex interplay of age, period, and cohort effects. Current health management policies demonstrate deficiencies in frailty prevention and psychosocial interventions. Findings underscore the imperative for age-appropriate, period-sensitive, and cohort-specific intervention strategies, particularly enhancing community-based health management, health literacy initiatives, and social support network optimization to address China's escalating aging challenges.