Association of C-reactive protein-triglycerides-glucose index-waist to height ratio and cardiometabolic multimorbidity in middle-aged and older adults: a nationwide cohort study

Background: Cardiometabolic multimorbidity (CMM) poses a severe global health burden. Effective prediction requires biomarkers capturing its complex pathophysiology, integrating inflammation, insulin resistance (IR), and central obesity. The C-reactive protein-triglycerides-glucose index-waist to height ratio (CTI-WHtR) is a composite index synthesizing these three pathways, but its longitudinal association with CMM risk remains unestablished. Methods: This prospective analysis utilized data from the China Health and Retirement Longitudinal Study (CHARLS). Cohort 1 (n = 8,875), free of CMM at baseline (2011), was established to assess the association between baseline CTI-WHtR and incident CMM. Cohort 2 (n = 5,807), a sub-cohort of longitudinal analysis, was analyzed to evaluate the impact of cumulative CTI-WHtR (cuCTI-WHtR) exposure (up to 2015) on CMM risk. The primary outcome was new-onset CMM (≥ 2 of diabetes, heart disease, or stroke). Cox proportional hazards models, restricted cubic splines, threshold analysis, and ROC curves were employed. Results: During the follow-up period, 873 and 490 incident CMM cases occurred in Cohort 1 and Cohort 2, respectively. After multiple adjustment, participants in the highest quartile of baseline CTI-WHtR had a 2.85-fold (95% CI 2.26–3.58) higher CMM risk compared to the lowest quartile (P < 0.001). A similar dose–response relationship was observed for cuCTI-WHtR (Q4 HR = 2.76, 95% CI 2.04–3.75). RCS analysis revealed a non-linear association with a significant inflection point. Both baseline and cumulative CTI-WHtR demonstrated superior predictive performance for CMM compared to its individual components (CTI or WHtR). Results remained robust across multiple sensitivity analyses. Conclusion: Both baseline and cumulative CTI-WHtR are strong, independent, and non-linear predictors of new-onset CMM. This integrative index, combining inflammation, IR, and central obesity, outperforms its components, offering a practical tool for early identification of high-risk individuals for targeted prevention. Graphical abstract: Supplementary Information: The online version contains supplementary material available at 10.1186/s12933-026-03151-x.