Diagnostic performance of TyG-related indices for MAFLD screening in older adults at moderate altitude: TyG-BMI showed the highest discriminatory ability

Abstract

Background: Triglyceride-glucose (TyG) index and its composite parameters have been proposed as surrogate indicators of insulin resistance. However, their association with metabolic dysfunction–associated fatty liver disease (MAFLD) among older adults living at moderate altitude remains insufficiently examined. The present study aims to investigate the association between TyG-related indices and MAFLD in this population and to identify the optimal screening indicator. Methods: Cross-sectional data were obtained from health examinations of older adults in a community in Lanzhou, China, during 2023–2024, comprising 3,547 residents aged ≥ 65 years. Univariate and multivariable logistic regression analyses were conducted to assess the association between TyG-related indices and MAFLD. Smooth curve fitting was applied to examine potential nonlinear relationships, and a two-piecewise linear regression model was used to further characterize nonlinearity. Receiver operating characteristic (ROC) analysis was employed to evaluate the predictive value of TyG-related indices for MAFLD risk. Results: A total of 2,986 community-dwelling adults aged ≥ 65 years from Lanzhou were included, with an overall MAFLD prevalence of 22.77%. After full adjustment for confounders, all TyG-related indices were significantly and positively associated with MAFLD risk in a dose-dependent manner. Restricted cubic spline analyses revealed significant nonlinear, J-shaped dose-response relationships for all four indices (TyG, TyG-BMI, TyG-WC, and TyG-WHtR; all P for nonlinearity < 0.05). Threshold effect analysis further identified saturation effects, particularly for TyG-BMI and TyG-WHtR, with the risk of MAFLD increasing sharply below their inflection points (266.44 and 5.59, respectively) but plateauing thereafter. Subgroup analyses revealed significant interactions. The associations of TyG-BMI, TyG-WC, and TyG-WHtR with MAFLD were stronger in males and non-diabetic participants (all P for interaction < 0.05). Receiver operating characteristic (ROC) analysis demonstrated that TyG-BMI had the best discriminative performance for MAFLD (AUC = 0.776, 95% CI: 0.757–0.795), which was statistically superior to TyG-WC (AUC = 0.737), TyG-WHtR (AUC = 0.730), and TyG (AUC = 0.672) (all P for comparison < 0.001). The optimal cut-off for TyG-BMI was 213.905, with a sensitivity of 77.1% and a specificity of 64.2%. Conclusions: In older adults at moderate altitude, TyG-related indices demonstrated valuable diagnostic performance for MAFLD screening. TyG-BMI showed the highest discriminatory ability (AUC = 0.776), statistically outperforming TyG-WC, TyG-WHtR, and the conventional TyG index. Its screening efficacy may be more pronounced in non-diabetic individuals. Therefore, TyG-BMI can serve as a simple, superior, and non-invasive screening tool for MAFLD in this population.