Associations of the triglyceride-glucose index, lipid-derived parameters, and their joint exposure with incident cardiometabolic multimorbidity: a nationwide prospective cohort study

The triglyceride-glucose (TyG) index and non-traditional lipid parameters (nTLPs) are accessible markers of cardiometabolic risk; however, their joint association with incident cardiometabolic multimorbidity (CMM) and the incremental predictive value of adding nTLPs to the TyG index remain unclear. This investigation utilized longitudinal datasets sourced from the China Health and Retirement Longitudinal Study (CHARLS), encompassing 7159 eligible participants. Kaplan–Meier analysis, multivariable Cox regression, and restricted cubic splines were used to evaluate associations between joint TyG–nTLP exposure and incident CMM. Subgroup and sensitivity analyses assessed robustness. Model discrimination and incremental predictive value were examined using receiver operating characteristic curves (ROC), net reclassification improvement (NRI), and integrated discrimination improvement (IDI). The median follow-up duration was 9 years, during which 758 participants developed CMM, corresponding to a cumulative incidence of 10.59%. Compared with participants in the dual-low groups for the TyG index and nTLPs, those in the dual-high groups had a higher risk of developing CMM. The corresponding fully adjusted hazard ratios (HRs) were 1.80 (95% CI 1.51–2.14) when both the TyG index and AIP were at high levels, 2.16 (95% CI 1.74–2.67) when both the TyG index and Non-HDL-C were at high levels, 2.10 (95% CI 1.72–2.57) when both the TyG index and CRI-I were at high levels, 2.05 (95% CI 1.66–2.53) when both the TyG index and CRI-II were at high levels, and 1.95 (95% CI 1.62–2.36) when both the TyG index and LCI were at high levels. Adding nTLPs to the TyG-based model resulted in only a modest incremental improvement in predictive performance. Among middle-aged and older adults, jointly elevated TyG index and nTLPs were associated with a higher risk of incident CMM, with the associations being more evident for incident diabetes and stroke than for incident heart disease. The combined assessment of the TyG index and nTLPs may provide complementary information for the early identification and risk stratification of individuals at elevated risk of CMM.