Systematic comparison of triglyceride-glucose (TYG)-index with other mortality predictive models in obese patients...

The Triglyceride-Glucose (TYG)-Index has been increasingly used as a simple surrogate marker of insulin resistance and has been associated with adverse cardiometabolic outcomes in several populations. TYG has gained great attention as a predictive index for mortality, but comparisons with other predictive indexes are unexplored, except for TYG-derived indexes such as TYG-body mass index (TYG-BMI).

We conducted a comparative prognostic study in two independent cohorts of adults with obesity: a general obesity cohort (n = 1,359) and a bariatric surgery cohort (n = 854), both with long-term follow-up approaching 14 years and with different mortality rates (11.5 vs. 5.5%, respectively). We compared TYG index, TYG-BMI index, blood glucose, age, Charlson Index, metabolic syndrome, glucose tolerance, diabetes mellitus, through Cox proportional hazard models with Harrell'C index, and through ROC analysis. We also evaluated the possible incremental predictive value of the above prognostic indexes when combined with blood glucose, the TYG-index, and TYG-BMI index.

Across both cohorts, several metabolic and clinical indices were significantly associated with all-cause mortality in univariable analyses. However, age and Charlson Comorbidity Index consistently showed the strongest discrimination and prognostic performance. The various indexes significantly predicted mortality at Cox proportional hazard models (p always < 0.001). Harrell'C index correlated with ROC area under the curves of each index (p < 0.001), and both Harrell and ROC correlated with quality indexes of Cox analysis (LR, p < 0.001) and with quality indexes of linear regression (F, p < 0.001). Findings were directionally consistent in the bariatric surgery cohort, although lower event rates attenuated overall discrimination. The combined use of more indices together was not uniformly useful to increase the predictive value of the above indices.

In obesity, TyG-based indices are associated with long-term mortality risk but add limited prognostic value beyond age and multimorbidity burden. These markers may be considered complementary tools for metabolic characterization rather than primary instruments for mortality risk stratification. This study reinforces the concept that various mortality indexes are as valid as, or even more predictive than, TYG index.