Association between atrial fibrillation and systemic inflammation with muscle mass and strength trajectories in old age

: The long-term impact of atrial fibrillation (AF) and systemic inflammation on muscle health and, hence, functional decline remains unclear. This study investigates the link between AF and longitudinal trajectories of muscle mass and strength, considering the role played by systemic inflammation. Data were obtained from 2048 participants (≥ 60 years) in the Swedish National Study on Aging and Care in Kungsholmen (SNAC-K), followed for 12 years. Muscle mass and strength were assessed using calf circumference, handgrip strength, and chair stand test. Inflammatory marker interleukin-6 (IL-6) and the stress-response mediator growth differentiation factor-15 (GDF-15) were measured at baseline. Linear mixed models examined the longitudinal changes in muscle outcomes according to AF status and the combination of AF status with inflammatory markers. Participants with AF experienced a steeper increase in the duration of the chair stand test (β = 1.49; 95% CI: 0.82 to 2.16). High levels of GDF-15 amplified declines in muscle mass (β =  - 0.12; 95% CI: - 0.20 to - 0.05) and chair stand test performance (β = 2.48; 95% CI: 1.66 to 3.30) in individuals with AF. Participants with AF and high IL-6 levels also experienced an accelerated decline of calf circumference (β =  - 0.12; 95% CI: - 0.19 to - 0.05) and chair stand test performance (β = 2.20; 95% CI: 1.39 to 3.01). AF is associated with a steeper decline in muscle mass and strength over time, exacerbated by elevated inflammatory biomarkers, underscoring the importance of systemic inflammation in AF-related functional decline.