**Background:** Patients with rheumatoid arthritis (RA) have elevated cardiovascular risk and are highly sedentary. The COVID-19 pandemic and associated social distancing measures threatened to further reduce physical activity and increase sedentary behavior in this vulnerable population. Prior evidence relied on self-report or smartphone step counts; no study had used validated posture-based accelerometry to objectively track changes in both activity and sedentary patterns before and during the pandemic in RA patients.
**Methods:** Thirty-five postmenopausal women with RA (mean age 60.9 years, 95% CI: 58.0–63.7; mean BMI 29.5 kg/m², 95% CI: 27.2–31.9) were recruited from an ongoing RCT at the University of São Paulo. All had baseline assessments prior to March 24, 2020 (the official start of social distancing in São Paulo). Follow-up assessments occurred between May 24 and July 7, 2020 (mean elapsed time 12.5 months). Physical activity and sedentary behavior were measured for 7 consecutive days (24 h/day) using activPAL micro™ accelerometers. Outcomes included time spent sitting/lying, prolonged sitting (≥30 min and ≥60 min bouts), standing, stepping, light-intensity PA (cadence <100 steps/min), moderate-to-vigorous PA (cadence ≥100 steps/min), and sit-stand transitions. Pain (Visual Analog Scale, 0–10), fatigue (Fatigue Severity Scale, 9–63), and health-related quality of life (SF-36, 0–100) were also assessed. Repeated measures mixed models were used with time as fixed factor and participants as random factor. Delta changes were correlated with changes in clinical outcomes using Pearson correlations.
**Key Results:** During social distancing, total stepping time decreased by 15.7% (−0.3 h/day, 95% CI: −0.4 to −0.1; p = 0.004), light-intensity PA decreased by 13.0% (−0.2 h/day, 95% CI: −0.4 to −0.04; p = 0.016), and moderate-to-vigorous PA decreased by 38.8% (−4.5 min/day, 95% CI: −8.1 to −0.9; p = 0.015). Total sedentary time did not change significantly (0.3 h/day, 95% CI: −0.4 to 1.0; p = 0.335), and standing time was unchanged (−0.1 h/day, 95% CI: −0.7 to 0.5; p = 0.767). However, time spent in prolonged sitting bouts ≥30 min increased by 34% (1.0 h/day, 95% CI: 0.3 to 1.7; p = 0.006), and bouts ≥60 min increased by 85% (1.0 h/day, 95% CI: 0.5 to 1.6; p < 0.001). Sit-stand transitions decreased by 10% (−5.1/day, 95% CI: −10.3 to 0.0; p = 0.051). No significant changes were observed in pain (mean change 0.31, 95% CI: −1.04 to 1.67; p = 0.652), fatigue (−2.3, 95% CI: −10.0 to 5.4; p = 0.550), physical quality of life (1.2, 95% CI: −8.2 to 10.7; p = 0.796), or mental quality of life (−9.3, 95% CI: −23.0 to 4.5; p = 0.183). Changes in activity and sedentary behavior were not significantly correlated with changes in any clinical outcome (all p > 0.050).
**Clinical Implications:** This study provides objective evidence that social distancing during COVID-19 shifted RA patients' activity patterns toward prolonged, uninterrupted sitting—a behavior independently linked to all-cause mortality and adverse cardiometabolic outcomes—even though total daily sitting time did not increase. The 38.8% reduction in MVPA is particularly concerning given RA patients' already elevated cardiovascular risk. The absence of short-term changes in pain, fatigue, or quality of life does not rule out longer-term consequences. The findings support recommending frequent breaks from sitting (e.g., 3 min of light walking every 30 min) as a pragmatic intervention for this population during periods of home confinement. Limitations include the small sample size (n=35), lack of medication/supplement tracking during the pandemic period, and inability to establish causality, though temporality and biological plausibility support the conclusions.