Association between serum cystatin C and chronic lung disease in middle-aged and elderly Chinese: a CHARLS cross-sectional study

The dose-response relationship between cystatin C (CysC) levels and chronic lung disease (CLD) development remains unclear and warrants further investigation. A more in-depth study of the relationship between serum CysC levels and CLD prevalence based on data from the China Health and Retirement Longitudinal Study (CHARLS). A cross-sectional analysis of 10,275 middle-aged and older adults aged 45 years and older was conducted using 2015 CHARLS data. Binary logistic regression models, restricted cubic spline curves (RCS), and threshold effects analyses were used to explore the association between different CysC levels and CLD prevalence in the middle-aged and older population, and subgroup analyses were performed to verify the robustness of the findings. When CysC was used as a categorical variable, the risk of CLD was increased by 38% in the T3 group compared with T1 (P < 0.001), and when CysC was used as a continuous variable, the risk of CLD was increased by 96% for each unit increase in CysC level (P < 0.001). In addition, there was a nonlinear relationship between CysC levels and the risk of CLD prevalence (P for non-linearity < 0.012), and the risk of CLD prevalence increased significantly with increasing CysC levels when CysC levels ≥ 0.754 mg/L. When CysC ≥ 0.754 mg/L, we need to be highly concerned about the risk of developing chronic lung disease in middle-aged and older populations, and those aged 45-64 years should be the focus of screening.