Association between intrinsic capacity and chronic lung disease among middle-aged and older adults: evidence from CHARLS and ELSA

BACKGROUND: Impaired Intrinsic capacity (IC) has been closely associated with the occurrence of various diseases. However, the relationship between impaired IC and chronic lung disease (CLD) remains unclear. This study aims to investigate the association between impaired IC and CLD among individuals aged 50 and above, as well as the potential country-specific differences. METHODS: This study utilized longitudinal follow-up data from the China Health and Retirement Longitudinal Study (CHARLS, 2011-2018) and the English Longitudinal Study of Ageing (ELSA, 2012-2018). Cox proportional hazards regression analyses were subsequently conducted to evaluate the association between IC impaired and risk of CLD. Subgroup analyses were performed to identify potential effect modifiers. The Restricted cubic splines (RCS)analysis was conducted to clarify whether there is a linear relationship between IC scores and CLD. RESULTS: A total of 7,897 participants were included, comprising 3,540 individuals from CHARLS and 4,357 from ELSA. The incidence of CLD was 10.6% in CHARLS and 3.1% in ELSA. After adjusting for covariates, participants with impaired IC exhibited a significantly higher risk of developing CLD compared to those with normal IC, with hazard ratio (HR) of 1.738 (95% confidence interval [CI], 1.371-2.205) in CHARLS and 1.983 (95% CI, 1.352-2.908) in ELSA. The results of the RCS analysis indicate that IC scores are negatively correlated with CLD (P for nonlinear > 0.05). Stratified analyses indicated that gender significantly modified this association in CHARLS (P for interaction < 0.05), whereas no such effect modification was observed in ELSA. Sensitivity analyses yielded results consistent with the primary analyses. CONCLUSION: Impaired IC among middle-aged and older adults is closely associated with the incidence of CLD in both CHARLS and ELSA. In the Chinese population, women exhibit a higher risk of developing CLD following impaired IC compared to men.