A significant proportion of patients with rheumatoid arthritis (RA) develop sarcopenia, according to a study published in the Modern Rheumatology. Aging, longer disease duration, joint destruction, and malnutrition are factors associated with the development of sarcopenia in this population.

Researchers of this cross-sectional study sought to determine the prevalence of sarcopenia in patients with RA and to characterize disease factors associated with sarcopenia. Sarcopenia is defined by the presence of low muscle mass, an absence of muscle strength, and low physical performance in the criteria set forth by the European Working Group on Sarcopenia in Older People (EWGSOP).

The study cohort included 388 consecutive female outpatients with RA who were admitted to the Kyoto University Hospital Rheumatic Disease Center from May 1 to December 31, 2014. Muscle mass was examined using bioimpedance analysis, muscle strength was tested using grip strength, and physical performance was evaluated using 6-minute walking speed. Patients were assessed for falls and bone fractures sustained in the year prior to study participation and had bone mineral density measured. The Kyoto University Rheumatoid Arthritis Management Alliance database was used to extract data on the participants’ age, disease duration, disease activity, treatments, Steinbrocker’s stage, Health Assessment Questionnaire Disability Index, and extra-articular manifestations. Nutritional state using the Mini Nutritional Assessment Short-Form and body mass index were further evaluated for evidence of malnutrition.

The prevalence of sarcopenia in the study cohort was 37.1% (14.7% had severe sarcopenia); 49% of the women had low muscle mass. In participants over 65 years, 51% were diagnosed with sarcopenia (21.7% with severe sarcopenia), and 60.1% had low muscle mass. Incidence of sarcopenia increased with age, from 14.0% in participants between 40 and 49 years to 78.6% for participants between 80 and 89 years. Patients with sarcopenia demonstrated significantly higher disease activity, advanced joint destruction, and lower Mini Nutritional Assessment Short-Form scores. Bone mineral density was higher in patients with vs without sarcopenia, as was the incidence of falls and fractures. However, the use of biological disease-modifying antirheumatic drugs (bDMARDs) was less frequent in patients with sarcopenia compared with patients without sarcopenia.

Logistic regression analyses were used to evaluate the association between characteristics of sarcopenia and RA, bone fractures, and falls. Researchers suggest that aging, longer disease duration, advanced radiological joint destruction, and malnutrition are associated with the development of sarcopenia in patients with RA. They also suggest that bDMARDs used to treat RA could suppress the development of sarcopenia in these patients.

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A limitation of examining sarcopenia in patients with RA is the difficulty in testing grip muscle strength, which in rheumatic patients may be associated with a limited grip motion due to pain or deformity. The cross-sectional design of the study limits the investigators’ ability to determine a causal relationship between sarcopenia and contributing factors. The EWGSOP criteria is only validated to assess primary sarcopenia; bioimpedance analysis used to measure muscle mass might not be as accurate as other methods. The study might have been limited by selection bias, as all the patients were treated at a single university facility focusing on RA.

Sarcopenia affects more patients with RA than the general population and may be indicated as a major complication of rheumatoid arthritis. Older patients living with rheumatoid arthritis and who experience decreased mobility due to joint destruction or malnutrition are at greater risk of developing sarcopenia. While antirheumatic therapies such as bDMARDs help suppress joint deterioration, they could also help prevent sarcopenia; further studies are needed to understand the underlying mechanisms and to develop effective therapies.

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Reference                                                                                                                       

Torii M, Hashimoto M, Hanai A, et al. Prevalence and factors associated with sarcopenia in patients with rheumatoid arthritis [published online August 9, 2018]. Mod Rheumatol. doi: 10.1080/14397595.2018.1510565