Body Mass Index Outperforms Triglyceride-Glucose Index in Predicting MAFLD in Type 2 Diabetes: A Cross-Sectional Mediation and Interaction Analysis.

BACKGROUND: The interplay between body mass index (BMI) and triglyceride-glucose (TyG) has yet to be systematically investigated on metabolic dysfunction-associated fatty liver disease (MAFLD) in type 2 diabetes mellitus (T2DM). This knowledge gap regarding the specific nature of their combined effects limits our ability to develop precise risk stratification algorithms and targeted intervention strategies. PURPOSE: This study aimed to investigate the independent and synergistic roles of BMI and TyG in MAFLD development among T2DM patients. METHODS: A cross-sectional study was conducted among 816 T2DM patients recruited from the Affiliated Hospital of Nanjing University of Chinese Medicine. MAFLD was diagnosed via Fibroscan. Dose-response relationships were assessed using restricted cubic splines (RCS). Multiplicative and additive interactions were evaluated using logistic regression models. Causal mediation analysis quantified the proportion of the BMI-MAFLD association mediated by TyG. Predictive performance was compared using receiver operating characteristic (ROC) curves. RESULTS: Among 816 participants, 528 (64.7%) had MAFLD. RCS confirmed linear positive associations of BMI and TyG with MAFLD. Compared to those with BMI <24 kg/m2, patients with BMI ≥28 kg/m2 had an adjusted odds ratio (aOR) of 6.94 (95% CI: 2.59-18.6). The highest TyG quartile had an aOR of 3.23 (95% CI: 1.08-9.64) vs the lowest. Mediation analysis suggested that TyG explained 7.5% of the observed association between BMI and MAFLD. Significant multiplicative interaction was observed (P < 0.05), whereas additive interaction was not significant. ROC analysis demonstrated that TyG had inferior discriminative ability (AUC: 0.679) compared to BMI (AUC: 0.784), with combined models (AUC: 0.796) providing minimal incremental value over BMI alone in identifying MAFLD. CONCLUSION: In T2DM, BMI exhibited a stronger association with MAFLD risk than TyG, with TyG accounting for a portion of this association but providing limited incremental improvement in discriminative ability.