Association Between the Triglyceride-to-HDL Cholesterol Ratio and Glycemic Control in Patients with Type 2 Diabetes Mellitus: A Real-World Retrospective Study

Background and Objectives: The triglyceride-to-high-density lipoprotein cholesterol ratio (TG/HDL-C) is a simple lipid index associated with insulin resistance and atherogenic dyslipidemia. Previous evidence has supported the TG/HDL-C ratio as a simple surrogate marker of insulin resistance and an adverse metabolic profile. However, its relationship with glycemic control in real-world patients with type 2 diabetes mellitus (T2DM) remains uncertain. This study evaluated the association between the TG/HDL-C ratio and poor glycemic control in patients with T2DM. Materials and Methods: This retrospective observational study included patients with T2DM followed in outpatient clinics. Poor glycemic control was defined as glycated hemoglobin A1c (HbA1c) ≥ 7%. The association between the TG/HDL-C ratio and glycemic control was assessed using group comparisons, Spearman correlation, tertile analysis, and multivariable logistic regression adjusted for age, sex, LDL-C, total cholesterol, insulin use, statin use, and fenofibrate use. Receiver operating characteristic (ROC) analysis was used to evaluate the discriminatory performance of the TG/HDL-C ratio for identifying poor glycemic control. A sensitivity analysis was performed after excluding patients receiving fenofibrate. Results: A total of 1001 patients with T2DM were included, of whom 568 (56.7%) had poor glycemic control. The mean age was 60.9 ± 11.4 years, and 57.1% of participants were women. The poor- and adequate-glycemic-control groups were comparable with respect to age and sex. The TG/HDL-C ratio was higher in patients with HbA1c ≥7% than in those with HbA1c < 7% [3.35 (2.35–5.00) vs. 2.74 (1.87–3.82), p < 0.001] and increased progressively across tertiles. In multivariable analysis, the TG/HDL-C ratio remained associated with poor glycemic control after adjustment for available covariates (OR: 1.201, 95% CI: 1.125–1.282, p < 0.001). The association remained significant after excluding fenofibrate users. ROC analysis showed modest discrimination (AUC: 0.601, 95% CI: 0.566–0.636). Conclusions: The TG/HDL-C ratio was associated with poor glycemic control in patients with T2DM, showing a graded association across tertiles. However, its standalone discriminatory performance is modest. Given its modest discriminatory performance, the TG/HDL-C ratio should not be considered a standalone diagnostic or predictive tool for poor glycemic control; rather, it may serve as an accessible adjunctive metabolic marker associated with an adverse glycemic and lipid profile.