Longitudinal Course of Muscle Status in Patients With Rheumatoid Arthritis
Toshifumi Fujiwara, Hidetoshi Tsushima, Osamu Tokunaga, Daisuke Hara, Yukio Akasaki, Ryosuke Yamaguchi, Ichiro Kurakazu, Yasuharu NakashimaABSTRACT
Objective
Muscle impairment is a common complication of rheumatoid arthritis (RA), but longitudinal data regarding its clinical course remain limited. This study aimed to evaluate the prevalence of muscle impairment and longitudinal changes in muscle status in patients with RA and to identify factors associated with muscle impairment.
Methods
This retrospective cohort study included 75 patients with RA who underwent assessment of skeletal muscle mass index (SMI) using bioelectrical impedance analysis and handgrip strength at baseline and follow‐up. Muscle status was classified according to the Asian Working Group for Sarcopenia 2025 criteria using handgrip strength and height‐adjusted SMI as normal muscle status, low muscle mass, possible sarcopenia, or sarcopenia. Patients with low muscle mass, possible sarcopenia, or sarcopenia were categorized as having muscle impairment. Baseline characteristics associated with muscle impairment were evaluated using logistic regression analysis. Longitudinal changes in SMI, handgrip strength, and muscle status were assessed over a median follow‐up of 29 months.
Results
At baseline, 20 patients (26.7%) had normal muscle status, whereas 55 (73.3%) had muscle impairment, including 30 (40.0%) with sarcopenia. Patients with muscle impairment were older and had lower body mass index (BMI), more advanced Steinbrocker stage, worse physical function, and lower health‐related quality of life than those with normal muscle status. In multivariable logistic regression analysis, older age (odds ratio [OR] 1.10, 95% confidence interval [CI] 1.03–1.20, p = 0.009) and lower BMI (OR 0.79, 95% CI 0.65–0.92, p = 0.005) were independently associated with muscle impairment. No significant changes in SMI or handgrip strength were observed during follow‐up. Among patients with normal muscle status at baseline, 78% remained normal at follow‐up, whereas 86% of those with muscle impairment continued to exhibit impaired muscle status.
Conclusion
Muscle impairment was highly prevalent in patients with RA and was independently associated with older age and lower BMI. No significant longitudinal changes in muscle status were detected during follow‐up, with most patients retaining their baseline muscle status classification. These findings provide longitudinal evidence that muscle impairment tends to persist in patients with established RA.