Triglyceride–Glucose Index and New-Onset Type 2 Diabetes Mellitus in Middle-Aged Men

Background: Type 2 diabetes mellitus (T2DM) is a major contributor to cardiovascular disease worldwide, with insulin resistance (IR) being a central pathophysiological mechanism. The triglyceride–glucose (TyG) index, derived from routine fasting measures, has emerged as a simple yet reliable proxy for IR and is increasingly recognised for its prognostic value in metabolic disorders. Despite growing interest, longitudinal evidence on TyG and incident T2DM, especially within European cohorts, remains limited and inconsistent. Therefore, we aimed to estimate the predictive role of TyG on the development of T2DM in an 8-year follow-up observation of a sample of adult men. Methods: We analysed data from 789 adult men without baseline T2DM, enrolled in the Olivetti Heart Study. Receiver operating characteristic curve analysis was used to determine the optimal TyG threshold for predicting new-onset T2DM. Results: Baseline TyG exhibited a strong, linear association with the subsequent development of T2DM. A TyG value above 4.88 was associated with an approximately twofold increase in risk, both before and after adjustment for confounding factors. Conclusions: The principal findings of this study indicate a significant predictive value of the TyG index in the development of new-onset T2DM. These observations suggest that the TyG index may serve as a low-cost, simple, and non-invasive tool for early cardio-metabolic risk assessment.