Objectives:
Rheumatoid arthritis (RA) is a chronic autoimmune disease that leads to rapid disability. Increased systemic inflammation, limited physical activity, and frequent glucocorticoid use in patients with RA can lead to sarcopenia, which is the loss of muscle strength, mass, and sometimes physical performance, thereby worsening the course of the primary disease, reducing productivity, and lowering quality of life. The aim of our study was to assess the state of skeletal muscle in patients with RA and evaluate its relationship with the course of the disease.

Material and methods:
The study included 120 patients with RA (women and men) and 30 control group participants. Skeletal muscle status was evaluated according to the criteria of the European Working Group on Sarcopenia in Older People (EWGSOP), 2019. Skeletal muscle status was determined using dual-energy X-ray absorptiometry. RA activity was evaluated using the DAS28, CDAI, and SDAI indices. Laboratory studies included determining the level of ESR and CRP.

Results:
The state of skeletal muscle was significantly worse in RA patients than in the control group. The most significant correlations were found between the risk of developing sarcopenia according to SARC-F, hand grip strength, chair stand test and appendicular skeletal mass (ASM) on the one hand, and DAS28 values on the other (r=0.57, r=-0.35, r=0.44, r=-0. 37, respectively, p<0.05). In contrast, a lower ASM index (ASMI) was significantly associated with higher CRP levels (r=-0.37, p<0.05) and was not associated with patients age or disease duration.

Conclusions:
The decrease in hand grip strength and skeletal muscle mass is not associated to the age of patients and disease duration. Instead, the values of all skeletal muscle parameters are closely associated with disease activity and the radiographic stage of RA.