Triglyceride glucose index—a body shape index (TyG-ABSI) outperforms traditional obesity indices in predicting all-cause and cardiovascular mortality in metabolic-dysfunction associated steatotic liver disease: the mediating role of biological aging

Metabolic dysfunction-associated steatotic liver disease (MASLD) is burdened by significant all-cause and cardiovascular mortality, yet simple and effective predictive indices for long-term outcomes are currently lacking. In this study, we investigated the prognostic value of the triglyceride glucose–a body shape index (TyG-ABSI), a novel composite of insulin resistance and visceral adiposity, for mortality in MASLD. This prospective cohort study included 7515 adults with MASLD from the National Health and Nutrition Examination Survey (NHANES, 1999–2018). MASLD was defined as a Fatty Liver Index ≥ 60 accompanied by at least one cardiometabolic risk factors. The primary outcomes were all-cause mortality (ACM) and cardiovascular mortality (CVM). Kaplan-Meier survival curves, multivariable Cox regression, restricted cubic splines (RCS), and receiver operating characteristic (ROC) analyses were employed to evaluate the predictive value of TyG-ABSI. Additionally, subgroup, sensitivity, and mediation analyses were conducted to verify robustness and explore underlying mechanisms. During a median follow-up of 138 months, 1368 all-cause and 376 cardiovascular deaths were recorded. TyG-ABSI demonstrated improved predictive accuracy compared to TyG, TyG-BMI, TyG-WC, and TyG-WHtR, as evidenced by higher AUC values and significant Net Reclassification Improvement（NRI). In fully adjusted models, participants in the highest TyG-ABSI quartile faced significantly elevated risks of ACM (HR 1.49, 95% CI 1.03–2.14) and CVM (HR 2.32, 95% CI 1.02–5.30) relative to the lowest quartile. RCS analysis indicated a linear dose-response relationship, and the associations remained robust across subgroup and sensitivity analyses. Mediation analysis revealed that accelerated biological aging significantly mediated mortality risks, with KDM and HD explaining 24.75% and 32.15% of ACM, and 34.89% and 46.53% of CVM, respectively. TyG-ABSI serves as a robust, independent predictor of mortality in patients with MASLD, outperforming traditional TyG-related metrics. The association is significantly associated with the pathway of accelerated biological aging, highlighting the utility of TyG-ABSI for enhanced risk stratification in clinical practice.