C-reactive protein–triglyceride–glucose index and incident cardiometabolic multimorbidity in middle-aged and older adults: a prospective analysis of the China Health and Retirement Longitudinal Study

Background: Cardiometabolic multimorbidity (CMM) is increasingly common in middle-aged and older adults. Biomarkers that jointly capture inflammation and insulin resistance for CMM risk stratification remain limited. Methods: We analyzed 7,785 adults aged ≥45 years from CHARLS (2011–2020). C-reactive protein–triglyceride–glucose index (CTI) was modeled continuously and by quartiles. Missing data were handled using multiple imputation. Cox proportional hazards models and restricted cubic splines were used to estimate associations and assess nonlinearity; prespecified interactions (age, hypertension, BMI) were tested. Predictive performance was evaluated using time-dependent area under the curve (AUC) / receiver operating characteristic (ROC) analyses, bootstrap internal validation, and reclassification beyond the WHO laboratory-based cardiovascular risk score (integrated discrimination improvement [IDI] and net reclassification improvement [NRI]). Prespecified sensitivity analyses assessed robustness.