
Background The triglyceride-glucose (TyG) related indices are simple biomarkers of insulin resistance and are associated with metabolic syndrome (MetS) and atrial fibrillation (AF). However, whether TyG-related indices are linked to all-cause and cardiovascular mortality in individuals with coexisting AF and MetS remains unclear. Methods We included 2535 participants with both AF and MetS from the UK Biobank. TyG-related indices, including TyG, TyG combined with body mass index (TyG-BMI), TyG combined with waist circumference (TyG-WC), and TyG combined with the waist-to-height ratio (TyG-WHtR), were calculated. The study endpoints were all-cause and cardiovascular mortality. Participants were followed until death or December 31, 2023, whichever occurred first. Associations between TyG-related indices and mortality outcomes were assessed using Cox proportional hazards models and restricted cubic spline (RCS) analyses. Results Over a mean follow-up period of 12.7 years (IQR: 11.8‒15.2), 956 all-cause deaths and 385 cardiovascular deaths were documented. Kaplan‒Meier survival analyses revealed the highest incidence of all-cause mortality in the fourth quartile of TyG (log-rank P