Multiple chronic conditions and intrinsic capacity among middle-aged and older adults: Evidence from CHARLS.

With the accelerating global aging process, maintaining intrinsic capacity (IC) among middle-aged and older adults has become a major public health priority. Multiple chronic conditions (MCC) are highly prevalent in later life and may contribute to declines in physical and mental functioning. However, evidence regarding the association between MCC and IC, as well as variations across disease types and socioeconomic contexts, remains limited. This study aimed to examine the association between MCC and IC among middle-aged and older adults and to explore heterogeneity across chronic disease categories, regional contexts, and individual characteristics. Data were obtained from the 2011, 2015, and 2018 waves of the China Health and Retirement Longitudinal Study. Using 28,613 pooled repeated cross-sectional person-wave observations, regression models incorporating survey-year and regional fixed effects were applied to examine the association between MCC and IC. Respondent-level cluster-robust standard errors were used to account for the nonindependence of repeated observations. Robustness analyses, instrumental variable estimation, and propensity score matching were conducted to assess the stability of the findings. Subgroup analyses were performed across macro-level (urban/rural residence and regional economic zones) and micro-level (sex, education, and household income) characteristics. MCC was significantly associated with lower IC (β = -0.076, P < .01). Disease-specific analyses showed that neurodegenerative diseases, including Parkinson disease and Alzheimer disease, demonstrated the strongest negative association with IC (β = -0.587, P < .01), followed by cardiovascular diseases (β = -0.135, P < .01). The negative association between MCC and IC was stronger among individuals living in rural areas and western regions, as well as among men, individuals with lower educational attainment, and those with lower household income. Robustness analyses, instrumental variable estimation, and propensity score matching yielded findings that were directionally consistent with the main analysis. MCC is significantly associated with reduced IC among middle-aged and older adults, with substantial heterogeneity across disease types and socioeconomic contexts. These findings highlight the importance of integrated chronic disease management, IC assessment, and targeted interventions for vulnerable populations, particularly those in socioeconomically disadvantaged regions, to promote healthy aging.