Lifestyle and body composition changes in patients with rheumatoid arthritis during the COVID-19 pandemic: A retrospective, observational study

**Background:** The COVID-19 pandemic led governments worldwide to implement behavioral restrictions, including stay-at-home orders and social distancing. Patients with rheumatoid arthritis (RA) already have lower baseline physical activity and higher sarcopenia prevalence than healthy individuals. This study aimed to investigate how these restrictions affected lifestyle, body composition, and muscle function in RA patients, and to identify factors associated with changes in activities of daily living (ADL) and exercise.

**Methods:** Data were drawn from the CHIKARA study, an observational study of 100 consecutive RA patients that began in 2016. Of these, 70 patients (57 women, 13 men) completed both the 4-year (January–March 2020, before restrictions) and 5-year (April–June 2021, after restrictions) follow-up visits. Body composition was measured using a TANITA MC-780A bioimpedance analyzer. Muscle function was assessed via grip strength (digital dynamometer) and 3-m gait speed. Disease activity was measured using DAS28-ESR and SDAI. Changes in ADL and exercise were self-reported using a visual analog scale (−100% to +100%), with pre-restriction levels set as 0. Statistical analysis used paired t-tests or Wilcoxon signed-rank tests for comparisons, and Spearman's correlation with multivariate linear regression (adjusted for age, DAS28-ESR, and mHAQ) to identify factors associated with changes in ADL and exercise.

**Key Results:** Muscle mass decreased significantly from 34.7 kg to 34.0 kg (p<0.001), and grip strength from 17.2 kg to 16.2 kg (p=0.026). Fat mass increased from 15.5 kg to 16.2 kg (p=0.014), and fat percentage from 28.6% to 30.4% (p=0.009). Disease activity (DAS28-ESR, SDAI, mHAQ, CRP, MMP3) showed no significant change. ADL decreased by a mean of 43.8% (median 39%), with 36% of patients reporting a reduction of more than half. Exercise decreased by a mean of 20.0% (median 0%), with 51% reporting no change. No patients reported increased ADL or exercise. On multivariate analysis, the change in muscle mass (β=−0.335, p=0.007) was the only independent factor associated with the change in exercise. No significant correlations were found between change in ADL and any body composition or muscle function variable.

**Clinical Implications:** The COVID-19 pandemic restrictions led to significant adverse changes in body composition and muscle function in RA patients, despite stable disease activity. The finding that muscle mass loss was independently associated with reduced exercise highlights the importance of maintaining physical activity even during periods of restricted movement. Clinicians should counsel RA patients to continue appropriate exercise during behavioral restrictions to prevent sarcopenia, falls, and loss of quality of life. The study is limited by its small sample size, lack of a healthy control group, and use of a non-validated Japanese-language questionnaire for ADL and exercise assessment.