Comparison of the triglyceride glucose index and triglyceride glucose-body mass index for predicting new-onset cardiovascular events in elderly patients with coronary heart disease: a retrospective cohort study

Elderly patients with coronary heart disease (CHD) are at elevated risk of the new-onset cardiovascular events (CVEs). Although the triglyceride-glucose (TyG) index and TyG-body mass index (TyG-BMI) are well-established predictors of cardiovascular events risk, the association between theses indices and the risk of new-onset CVEs in elderly patients with CHD remains unclear. Thus, this study aimed to compare the predictive performance of the TyG index and TyG-BMI index for new-onset CVEs in elderly patients with CHD. This dual-center retrospective study consecutively enrolled 542 elderly patients with CHD from January 2016 to December 2023. The TyG and TyG-BMI indices were calculated and categorized into quartiles for analysis, with new-onset CVEs defined as the primary endpoint. Considering the relatively high event incidence in our cohort, modified Poisson regression with HC3 robust sandwich variance was applied to evaluate the associations of TyG and TyG-BMI with new-onset CVEs, instead of conventional logistic regression to avoid overestimation of effect sizes. Restricted cubic spline (RCS) analysis was performed to explore potential dose-response relationships. Additionally, C-index, net reclassification improvement (NRI), integrated discrimination improvement (IDI), and decision curve analysis (DCA) were utilized to quantify the incremental predictive value and clinical net benefit of the two indices beyond traditional cardiovascular risk factors. Over a 2-year follow-up period, the overall new-onset CVEs incidence was 40.96%. The TyG index, but not TyG-BMI, was significantly associated with a higher risk of new-onset CVEs. In the fully-adjusted modified Poisson regression model, the relative risk (RR, 95% CI) of new-onset CVEs was 1.56 (1.14–2.15) for TyG quartile 4 and 1.14 (1.03–1.27) per-SD increment in TyG. For TyG-BMI, the corresponding RR was 1.17 (0.86–1.58) for quartile 4 and 1.05 (0.94–1.17) per-SD increment, both non-significant. RCS analyses demonstrated a linear dose-response relationship between TyG and new-onset CVEs, without obvious nonlinearity. Adding TyG to the baseline risk model yielded statistically significant continuous-NRI (0.186, P = 0.026), while the increment in C-index was not statistically significant (DeLong test, P = 0.124), and IDI showed a borderline improvement ( P = 0.057). DCA showed only marginal gain in clinical net benefit. By contrast, adding TyG-BMI produced no significant improvement in predictive performance. A significant age-interaction was detected for TyG-BMI, with positive association limited to participants younger than 75 years. In elderly Chinese patients with CHD, the TyG index showed superior predictive performance for new-onset CVEs relative to TyG-BMI, was only associated with CVEs among patients younger than 75 years. The TyG index may represent a cost-effective biomarker for risk stratification, although its incremental clinical benefit remains modest.