Changes in physical activity measured by accelerometry following initiation of DMARD therapy in rheumatoid arthritis

Abstract

The aim of this study was to assess changes in habitual physical activity levels in response to DMARD therapy in RA patients. Eighteen drug-naive RA patients were prospectively assessed at baseline and following 3 months of DMARD therapy for habitual physical activity by accelerometry, disease activity using the clinical disease activity index (CDAI) and functional disability using the modified HAQ (mHAQ). Baseline physical activity was also compared with an equal number of healthy control participants matched for age, sex and BMI. Following 3 months of DMARD therapy, in parallel with significant improvements in CDAI scores (P < 0.001) and HAQ scores (P < 0.001), accelerometry measures in the RA cohort showed that the average activity counts in sedentary thresholds decreased (P = 0.012), while average activity counts within higher-intensity thresholds increased (P = 0.039). Multiple regression analysis showed that the change in moderate activity was associated with a decrease in CRP (β = - 0.922, P = 0.026) while the decrease in sedentary activity and increase in moderate activity were associated with decreased morning stiffness of the joints (β = 0.694, P = 0.035 and β = -0.927, P = 0.024, respectively). At baseline, RA patients were less physically active than control participants in the morning (P = 0.048) and in the late afternoon (P = 0.016), but these diurnal differences were no longer significant after the DMARD intervention. These findings suggest that accelerometry may potentially be a viable objective method of assessing changes in physical disability in response to various disease-modifying drugs.