TyG-BRI, frailty, and all-cause mortality in older adults with atrial fibrillation without diabetes: a two-cohort study

Metabolic dysregulation and frailty are both associated with adverse outcomes in atrial fibrillation (AF), but their combined associations with mortality among older adults with AF remain unclear. We investigated the independent and joint associations of the triglyceride-glucose–body roundness index (TyG-BRI) and frailty status with all-cause mortality in older adults with AF without diabetes. We analysed data from two prospective cohorts: the UK Biobank (n = 2573) and a community-based AF cohort from Jiangdu, China (n = 803). Participants were categorized according to TyG-BRI tertiles and frailty status (robust vs. non-robust). Multivariable Cox regression, restricted cubic spline analyses, and predictive performance analyses were performed. During follow-up, 969 and 179 deaths occurred in the UK Biobank and Jiangdu cohorts, respectively. TyG-BRI showed significant nonlinear associations with all-cause mortality in both cohorts. In categorical analyses, only high TyG-BRI was significantly associated with increased mortality in the UK Biobank, whereas both low and high TyG-BRI were associated with increased mortality in the Jiangdu cohort. Frailty status was consistently associated with increased mortality risk across populations. Joint analyses demonstrated that non-robust participants with abnormal TyG-BRI levels had the highest mortality risk. The incremental predictive performance of the combined assessment was modest and varied between cohorts. Among older adults with AF without diabetes, TyG-BRI and frailty status were associated with all-cause mortality, and their joint assessment identified subgroups with different levels of mortality risk. These findings suggest that TyG-BRI and frailty may provide complementary prognostic information in this population. What is already known on this topic? Metabolic dysregulation and frailty are both associated with adverse outcomes in older adults with atrial fibrillation, but their combined impact on mortality risk remains unclear. What this study adds? In two independent cohorts from the UK and China, TyG-BRI showed a nonlinear association with all-cause mortality, and joint assessment of TyG-BRI and frailty identified high-risk subgroups. How this study might affect research, practice or policy? These findings support further evaluation of combined metabolic and frailty assessment for mortality risk stratification in older adults with AF without diabetes.