POS0471 CONTINUOUSLY LOW MUSCLE MASS CONTRIBUTES TO WORSE PHYSICAL FUNCTION IN RHEUMATOID ARTHRITIS PATIENTS: A 5-YEAR FOLLOW-UP STUDY
Authors: J. Pan, Y. W. Zou, Z. M. Ouyang, J. D. MA, J. Z. Lin, P. W. Jia, H. W. Zheng, Y. Yang, L. Dai
Journal: Annals of the Rheumatic Diseases (2024)

<h3>Background:</h3> Rheumatoid arthritis (RA) is characterized with joint damage and physical dysfunction, leading to reducing quality of life. The causes of physical dysfunction in RA are multifactorial, including disease activity, joint pain, and joint deformity. Recent studies have reported that baseline sarcopenia is associated with long-term physical activity restriction in general population. Our previous cross-sectional and one-year follow-up study showed that low muscle mass is common in Chinese patients with RA and is associated with poor physical function. Surprisingly, the muscle mass only increased slightly across 1-year follow-up. There were no other published studies with longer prospective follow-up about the dynamic change of muscle mass in RA patients. <h3>Objectives:</h3> To investigate the trajectory of muscle mass over 5-year follow-up and its impact on longitudinal changes of physical function in RA patients. <h3>Methods:</h3> Our real-world prospective RA cohort recruited patients from September, 2015 which conducted at the Department of Rheumatology and Immunology, Sun Yat-Sen Memorial Hospital, China. Those who finished at-least 5 years followed up were eligible in this study. Clinical data, including RA disease activity (DAS28-ESR, DAS28-ESR, SDAI and CDAI) and physical function indicator (HAQ-DI), were collected at baseline and visits at 3, 6, 12, 24, 36, 48 and 60 months. Physical dysfunction was indicated as HAQ-DI &gt; 0. Body composition was assessed by bioelectric impedance analysis annually, including percentage of body fat mass (PBF) and appendicular skeletal muscle mass index (ASMI). Myopenia was defined by ASMI≤ 7.0 kg/m<sup>2</sup> in men and ≤ 5.7 kg/m<sup>2</sup> in women, while overfat was defined by the PBF ≥ 25% in men and ≥ 35% in women, respectively. The transitions of muscle and fat status across 5-year follow-up were displayed alluvial plot and transition probabilities were estimated through continuous-time multistage Markov modelling. Generalized estimating equation (GEE) analysis was performed to evaluate the longitudinal relations between time-varying ASMI/PBF and HAQ-DI. <h3>Results:</h3> ①A total of 288 RA patients were enrolled. RA patients had a mean age of 49.4±11.2 years, and 245 (85.1%) were females. The median RA disease duration was 52 (IQR 24-108) months. ②There were 229 (79.5%) RA patients with active disease (CDAI &gt; 2.8) at baseline. Under treat-to-target strategy, RA disease activity improved significantly with CDAI remission rates 37.3% at 3 months, 40.7% at 6 months, and remained 37.0%-39.4% in the subsequent 5-year follow-up (Figure 1A). Meanwhile, the physical function improved significantly with the rate of physical dysfunction decreased from 62.3% at baseline to 42.7% at 3 months, 41.8% at 6 months, and remained 38.8%-43.9% in the subsequent follow-up (Figure 1B). ③At baseline, there were 38.2% patients with myopenia. Surprisingly, there were no significant change of ASMI, PBF, BMI or the rate of myopenia over time (Figure 1C-F). ④In the longitudinal analysis using GEE, ASMI was negatively associated with HAQ-DI over time [model 1: OR = 0.931, 95% CI (0.887-0.978), P = 0.004]. After adjusting for gender, age, active smoking, disease duration, RF status, ACPA status, comorbidities, and previous treatments, ASMI was still negatively associated with HAQ-DI [model 2: OR = 0.928, 95% CI (0.885-0.972), P = 0.002] and remained significant for further adjusting for time-varying CDAI [model 3: OR = 0.959, 95% CI (0.926-0.993), P = 0.017, Table 1]. <h3>Conclusion:</h3> Our study first illustrates muscle mass remains stable over 5-year follow-up in RA patients, though disease activity and physical function have been significantly improved. Low muscle mass is associated with worse physical function over time in RA. The results imply the importance to improve muscle mass in RA. <h3>REFERENCES:</h3> <b>NIL.</b> <h3>Acknowledgements:</h3> <b>NIL.</b> <h3>Disclosure of Interests:</h3> <b>None declared.</b>