To explore the association between the serum creatinine-to-cystatin C ratio (CCR) and incident chronic pulmonary disease provide clinical evidence for the early intervention and treatment of lung diseases.

Based on data from the China Health and Retirement Longitudinal Study (CHARLS) collected between 2015 and 2018, the middleaged and elderly population without pulmonary disease in 2015 was used as the baseline, and followed up on pulmonary disease outcomes in 2018. Multivariable Cox proportional hazards regression was performed to assess the association of CCR with incident chronic pulmonary disease, with hazard ratios (HR) and 95%CI estimated. In the regression model, restricted cubic spline plots were used to explore the changing trend of the relationship between CCR and incident chronic pulmonary disease. Subgroup analysis was conducted based on the analysis of the multivariable Cox proportional hazards regression model.

A total of 8 366 subjects were included in the study. Among them, 657 individuals (7.9%) diagnosed with incident chronic pulmonary disease were divided into CCR-1, CCR-2, CCR-3, and CCR-4 groups according to the quartiles of CCR. Multivariable Cox proportional hazards regression analysis showed that, compared with the CCR-1 group, the multivariableadjusted HR(95%CI) for the CCR-2, CCR-3, and CCR-4 groups were 1.049 (0.847-1.300), 0.997 (0.793-1.254), and 0.700 (0.538-0.911), respectively. Restricted cubic spline analysis revealed a clear dose-response association of CCR with incident chronic pulmonary disease, and higher CCR was associated with a significantly lower risk of disease onset. No significant nonlinear trend was detected (overall P < 0.05 and nonlinearity P > 0.05). Subgroup analyses revealed no significant interactions between CCR and sex, age, hypertension, diabetes, or history of drinking and smoking (P > 0.05).

Higher CCR levels were significantly associated with a lower risk of incident chronic pulmonary disease, indicating a significant inverse association.