Triglyceride–HDL cholesterol–glucose body index and cardiometabolic multimorbidity: evidence from a national longitudinal cohort and a subplateau health-screening population

Background Cardiometabolic multimorbidity (CMM) is an increasing health burden, but accessible composite markers integrating glycemic, lipid, and adiposity-related abnormalities remain insufficiently evaluated across heterogeneous populations. We examined the association between the triglyceride–high-density lipoprotein cholesterol–glucose body index (TyHGB) and CMM in two distinct Chinese populations. Methods This study included 8,116 participants without baseline CMM from the China Health and Retirement Longitudinal Study (CHARLS) and 10,092 adults undergoing routine health examinations in a southwestern China subplateau region. Cox proportional hazards models were used to evaluate incident CMM in CHARLS, whereas logistic regression was used for prevalent CMM in the health-screening population. TyHGB was analyzed per standard deviation and by quartiles. Nonlinear associations, subgroup consistency, discriminatory performance, exploratory mediation, and robustness were further assessed. Results During follow-up, 632 CHARLS participants developed CMM (7.8%), while 941 participants in the health-screening population had prevalent CMM (9.3%). Compared with the lowest quartile, the fully adjusted hazard ratio for the highest TyHGB quartile was 2.92 (95% CI, 2.19–3.89) in CHARLS, and the corresponding odds ratio was 11.62 (95% CI, 8.82–15.3) in the health-screening population (both P for trend <0.001). Nonlinear associations were observed in both populations, with inflection points of 9.139 and 10.470, respectively. TyHGB showed modestly higher AUCs than TyG in CHARLS (0.689 vs 0.648) and the health-screening population (0.762 vs 0.710; both P < 0.001). Associations were consistent across major subgroups and sensitivity analyses. In CHARLS, exploratory mediation analysis estimated that HbA1c accounted for 48.15% of the association. Conclusions Higher TyHGB was consistently associated with greater CMM burden across longitudinal and cross-sectional settings. As a low-cost index derived from routine measurements, TyHGB may serve as a useful adjunct to established cardiometabolic risk indicators in population-level screening, and its clinical role warrants further prospective evaluation; its thresholds and performance should be interpreted within the target population.