Joint association of frailty index and biological age with chronic obstructive pulmonary disease: a cohort study from CHARLS

Chronic Obstructive Pulmonary Disease (COPD) is associated with frailty and ageing, but there is insufficient evidence from existing longitudinal studies. This research explored the longitudinal association between frailty, ageing and COPD. We used the China Health and Retirement Longitudinal Study (CHARLS) data to perform a cohort study. The study population was non-COPD patients in wave 1 (2011), and the outcome was the occurrence of COPD at the end of follow-up (wave 4-wave 5). Frailty was assessed using the CHARLS modified frailty index (CMFI), and ageing was evaluated using the biological age (BA). We used multivariate logistic regression to examine the longitudinal associations between CMFI and BA with COPD. Fitted curves were used to analyze the dose-response relationship of CMFI and BA with COPD. A 3D surface diagram was used to analyze the association between BA and CMFI with COPD. In addition, subgroup and sensitivity analyses were performed. 6452 non-COPD patients were enrolled in the study, and after follow-up, 616 participants were diagnosed with COPD. Logistic regression and fitted curves showed a positive correlation between CMFI and BA and the development of COPD. The risk of COPD increased by 19% for every one standard deviation (SD) increase in BA and 32% for every one SD increase in CMFI. A 3D surface diagram shows a joint association between CMFI and BA with the COPD. Subgroup and sensitivity analysis results are stable. This study found a joint association between CMFI and BA with COPD, suggesting that CMFI and BA are risk factors for the development of COPD.