Reassessment-stage metabolic indices and subsequent cardiorenal outcomes in adults with diabetes: CHARLS and an independent hospital validation cohort.

BACKGROUND: Simple metabolic indices may capture residual cardiorenal risk beyond conventional glycemic markers, but their reassessment-stage value and external reproducibility remain unclear. We evaluated the triglyceride-glucose (TyG) index, metabolic score for insulin resistance (METS-IR), triglyceride total cholesterol body weight index (TCBI), and cholesterol-high-density-lipoprotein-glucose (CHG) index in relation to subsequent cardiorenal outcomes. METHODS: The CHARLS cohort comprised participants with diabetes identified in 2011 who attended the 2015 survey, remained free of overt cardiorenal outcomes, and had post-2015 follow-up. The primary outcome was the first cardiovascular or kidney event. Analyses included survey-wave-based Cox and discrete-time models, Kaplan-Meier curves, restricted cubic splines, selection weighting, proportional-hazards diagnostics, 10-fold cross-validated calibration and decision curves, and replication in an independent hospital validation cohort. RESULTS: The eligible CHARLS reassessment cohort included 1,104 participants and 311 composite cardiorenal outcomes; glycemia-adjusted complete-case Cox analyses included 787-800 participants. Each 1-SD increase in TyG, TCBI, and METS-IR was associated with higher risk, with HRs (95% CIs) of 1.26 (1.06-1.49), 1.19 (1.03-1.37), and 1.20 (1.04-1.38), respectively, whereas CHG was not significant. Selection-weighted and discrete-time estimates were similar, and proportional-hazards tests showed no violations. In the wave-approximated 4-year prediction sample (N = 749; 173 events), apparent AUC gains were small and not statistically significant; 10-fold cross-validated AUC increased only from 0.665 to 0.669-0.671, without a consistent decision-curve advantage. In the independent hospital validation cohort (N = 1,578; 296 events), with post-landmark follow-up administratively censored at 4 years, positive composite-outcome associations were reproduced for TyG, TCBI, and METS-IR, whereas CHG showed a weaker and graphically inconsistent pattern. CONCLUSIONS: Among adults with diabetes identified in 2011 who returned for the 2015 CHARLS reassessment and remained free of overt cardiorenal outcomes, higher TyG, TCBI, and METS-IR were associated with subsequent composite cardiorenal outcomes. Robustness analyses supported these associations, whereas predictive improvement was limited. These indices may serve as exploratory, low-burden adjunctive markers at reassessment, with supportive independent clinical validation; clinical utility requires further study.