Sarcopenia in Atrial Fibrillation: A Risk Factor for Adverse Outcomes in a UK Biobank Study

Abstract Background and Aims Sarcopenia, characterized by reduced muscle mass and function, has been increasingly implicated in cardiovascular disorders. However, its prognostic relevance in atrial fibrillation (AF) remains unclear. This study evaluated the association between sarcopenia and adverse outcomes in individuals with AF using UK Biobank data. Methods This retrospective cohort study included individuals with AF enrolled between 2006 and 2010 at 22 centers. Sarcopenia was defined per European Working Group on Sarcopenia in Older People 2 (EWGSOP2) criteria as low muscle strength and/or low muscle mass measured by handgrip and bioelectrical impedance analysis. Propensity score weighting adjusted for baseline differences. The primary outcome was a composite of all-cause mortality, major bleeding, thromboembolic events (stroke/systemic embolism), and heart failure admission; each component was also assessed individually. Results Among 5,144 patients with AF (median age, 64.0 years; 24.1% female), 16.7% had sarcopenia. After propensity score weighting, sarcopenia was associated with a higher incidence of the primary composite outcome (43.9 per 1,000 person-years [PYRs]), with an adjusted hazard ratio [HR] of 1.30 (95% confidence interval [CI], 1.15–1.46). This risk was mainly driven by elevated rates of all-cause mortality (26.4 per 1,000 PYRs; aHR, 1.44; 95% CI, 1.24–1.68) and major bleeding (14.4 per 1,000 PYRs; aHR, 1.34; 95% CI, 1.10–1.65). Subgroup analyses demonstrated consistent results. Conclusion Even after PS-weighting analysis, some residual confounders may remain; however, sarcopenia was independently associated with adverse clinical outcomes, particularly mortality and bleeding risk. Screening for sarcopenia may enhance risk stratification and management, particularly in patients receiving anticoagulation.