The clinical utility of accelerometry in patients with rheumatoid arthritis.

OBJECTIVES: To assess habitual physical activity levels in patients with RA compared with healthy control participants and to compare these measures with health-related quality of life and disease activity in the RA patients. METHODS. Fifty RA patients [age 48 (13) years] and 22 BMI, sex and geographically matched control participants were recruited. Habitual physical activity was measured using an Actical accelerometer worn on the hip for 2 consecutive weeks. Patients completed the Short Form-36 (SF-36) and modified Health Assessment Questionnaires (HAQ-DI). Disease activity was assessed using the Simplified Disease Activity Index (SDAI). RA patients were further categorized as more physically active (n = 25) and less physically active (n = 25) according to their average activity counts.
RESULTS: The RA group spent more time in sedentary activity than the control group (71% vs 62% of the day respectively, P = 0.002) and had bimodal decreases in diurnal physical activity compared with the control group in the morning (P < 0.001) and late afternoon (P < 0.001). HAQ-DI, when adjusted for age and disease duration, was negatively correlated with physical activity in the RA group (r = -0.343, P = 0.026). The more physically active patients scored better than the less physically active patients on every component of the SF-36.
CONCLUSION: Patients with RA lead a significantly more sedentary lifestyle than healthy controls and show diurnal differences in physical activity due to morning stiffness and fatigue. Higher levels of habitual physical activity may be protective of functional capacity and are highly associated with improved health-related quality of life in RA patients.