Novel anthropometric and metabolic indices for identifying insulin resistance and body-composition abnormalities in elderly patients with type 2 diabetes: a cross-sectional study

Background Insulin resistance (IR) and abnormalities in body composition are common in older adults with type 2 diabetes mellitus (T2DM), but the optimal screening indices remain uncertain. We compared anthropometric and metabolic composite indices for identifying IR, visceral obesity and dynapenia in this population. Methods This cross-sectional study included 127 hospitalised patients with T2DM aged 65–80 years. Body Roundness Index (BRI), A Body Shape Index (ABSI), the triglyceride-glucose (TyG) index and its derivatives (TyG-WC, TyG-WHtR and TyG-BMI), visceral adiposity index, lipid accumulation product, neck-to-waist ratio and neck circumference were calculated. IR was defined as HOMA-IR ≥ 2.0, visceral obesity as visceral fat area ≥ 100 cm ² , and dynapenia as grip strength < 28 kg in men or < 18 kg in women. Associations were analysed using Spearman's correlation, multivariable logistic regression per 1-SD increment, and receiver operating characteristic curve analysis with DeLong comparisons and bootstrapped confidence intervals. Results IR was present in 68.5% of patients, visceral obesity in 38.6% and dynapenia in 28.3%, whereas sarcopenia was rare (0.8%). TyG-WC showed the strongest correlation with HOMA-IR (ρ = 0.347, p < 0.001) and the highest AUC for IR (0.660, 95% CI 0.568–0.761), although it was not significantly superior to the basic TyG index (AUC 0.654; DeLong p = 0.897). After adjustment for age, sex and BMI, only TyG-based indices remained independently associated with IR: TyG-WC (OR 2.186), TyG-WHtR (OR 1.995), TyG (OR 1.706) and TyG-BMI (OR 1.684), all p ≤ 0.023 per 1-SD increment. For visceral obesity, waist circumference had the highest AUC (0.875), followed by BMI (0.809) and neck circumference (0.792); BRI was the strongest independent predictor (OR 6.480 per 1-SD increment, p < 0.001). Only TyG-based indices were significantly correlated with HbA1c. Conclusions In older adults with T2DM, TyG-based indices, particularly TyG-WC, were the only indices independently associated with IR, although their advantage over the basic TyG index was not significant and their absolute discriminatory performance was modest. Waist and neck circumference are practical bedside markers of visceral obesity. The contrast between frequent dynapenia and rare sarcopenia highlights the value of grip-strength assessment in geriatric diabetes care.