Impaired Physical Function And Altered Muscle Biomechanical Properties In Patients With Early Rheumatoid Arthritis

Patients with long-standing rheumatoid arthritis (RA) commonly develop skeletal muscle disease defined by impaired function, sarcopenia, and physical disability. In early RA patients (< 6 months after disease onset), skeletal muscle health and physical function are understudied. PURPOSE: To identify if patients with early RA have impaired skeletal muscle health and physical function compared to matched controls. METHODS: Early RA (n = 10) and age-, BMI-, sex-matched, sedentary control (n = 10) participants underwent cross-sectional assessments. Self-reported health was assessed via the Patient-Reported Outcomes Measurement Information System (PROMIS). Passive biomechanical properties — tone, stiffness, and elasticity — of bilateral biceps brachii, forearm flexor, vastus lateralis, and tibialis anterior muscles were assessed with the MyotonPro® device. Body composition (BOD POD®), cardiorespiratory fitness, and strength (hand grip and isometric knee extension) were also assessed. Myotonometry measures were analyzed using principal component analysis using scores with >2 factor components. Outcomes were compared using two sample t-tests and Spearman correlations. RESULTS: Compared to matched controls, early RA patients had lower self-reported physical function and physical health, muscle tone and stiffness, and grip strength (Table 1). Early RA muscle tone and stiffness (Myotonometry-Factor 1) were negatively correlated with prednisone use for RA management (rho = -0.72, p = 0.02). Lower limb muscle elasticity (Myotonometry-Factor 3) was negatively correlated with RA disease duration (rho = -0.64, p = 0.04). CONCLUSIONS: In exploratory analyses, early RA patients report poorer physical function and exhibit muscle health and performance deficits. Assessment of skeletal muscle biomechanical properties may be a useful clinical tool to evaluate the effects of RA — even at early stages — on skeletal muscle and physical function. Gilead Sciences Inc. provided funding to Duke University for investigator-initiated research related to this project.