Reduced skeletal muscle independently predicts 1-year aggravated joint destruction in patients with rheumatoid arthritis

Background: Numerous cross-sectional studies have reported the associations between rheumatoid arthritis (RA) and reduced skeletal muscle. We firstly explored the dynamic change of skeletal muscle and its effect on RA clinical outcomes in a real-world prospective cohort. Methods: Consecutive RA patients were treated according to the treat-to-target strategy and completed at least 1-year follow up. Clinical data and muscle index (assessed by bioelectric impedance analysis) were collected at baseline and visits at 3, 6, 9 and 12 months. Myopenia was defined by appendicular skeletal muscle mass index <= 7.0 kg/m(2) in men and <= 5.7 kg/m(2) in women. A 1-year radiographic progression as primary outcome was defined by a change in the total Sharp/van der Heijde modified score > 0.5 units. Results: Among 348 recruited patients, 315 RA patients (mean age 47.9 years, 84.4% female) completed 1-year follow up. There were 143 (45.4%) RA patients showing myopenia at baseline. Compared with those without baseline myopenia, RA patients with baseline myopenia had higher rate of 1-year radiographic progression (43.4% versus 21.5%, all p < 0.05). Baseline myopenia was an independent risk factor for 1-year radiographic progression with adjusted odds ratio (AOR) of 2.5-fold, especially among RA patients in remission at baseline both defined by Disease Activity Score in 28 joints (DAS28) including C-reactive protein (DAS28-CRP) or erythrocyte sedimentation rate (DAS28-ESR) with AOR of 18.5-42.9-fold. Further analysis of six subtypes of dynamic skeletal muscle change showed that newly acquired myopenia at endpoint was associated with radiographic progression (AOR of 5.4-fold). Conclusions: Reduced skeletal muscle is an independent predicting factor for 1-year aggravated joint destruction, especially in remission RA. The importance of dynamic monitoring of skeletal muscle and muscle improvement therapy are worth exploration.