[Clinical characteristics of overlapping syndromes of low muscle mass in patients with rheumatoid arthritis and their impact on physical function].

Objective: To investigate the clinical characteristics of overlapping syndromes of low muscle mass in Chinese patients with rheumatoid arthritis (RA) and their impact on physical function.

Methods: Consecutive patients with RA were recruited from September 2019 to April 2024 at Department of Rheumatology and Immunology, Sun Yat-Sen Memorial Hospital. Clinical data including disease acti-vity, physical function and radiographic assessment were collected. All patients also finished measurement of body composition, grip strength, and gait speed, and overlapping syndromes of low muscle mass as well as malnutrition, sarcopenia, sarcopenic obesity, and cachexia were evaluated. The Stanford health assessment questionnaire- disability index (HAQ-DI) was used to evaluate physical function. Logistic regression was used to analyze the related factors of physical dysfunction.

Results: A total of 1 016 RA patients were recruited. Their mean age was (52.4±12.5) years, and 82.5% were female. There were 557 cases (54.8%) with overlapping syndromes of low muscle mass and all of them were malnutrition. On this basis, 326 cases (32.1%) exhibited sarcopenia, 124 (12.2%) sarcopenic obesity, and 33 (3.2%) cachexia. There were 584 (57.4%) of RA patients having physical dysfunction, with varying degrees of severity 421 (41.4%) mild, 124 (12.2%) moderate, and 39 (3.8%) severe. Compared with patients without overlapping syndromes of low muscle mass (n=459) or with malnutrition only (n=231), RA patients with both malnutrition and sarcopenia (n=326) had significantly higher core disease activity indicators and higher rate of physical dysfunction (69.6% vs. 42.0% vs. 56.6%). However, compared with patients without overlapping syndromes of low muscle mass, patients with malnutrition only had lower HAQ-DI score (median 0.0 vs. 0.1) and lower rate of physical dysfunction (42.0% vs. 56.6%). Multivariate Logistic regression analysis showed that simultaneously overlapping malnutrition and sarcopenia were associated factors of physical dysfunction (OR=2.021, 95%CI: 1.067-3.828), but malnutrition only was not.

Conclusion: Simultaneously overlapping malnutrition and sarcopenia can deteriorate disease activity and physical dysfunction in RA patients. The screening and evaluation of overlapping syndromes of low muscle mass, especially sarcopenia should be emphasized in patients with RA.