Objectives: The aims of this study were to study physical activity (PA) in patients with RA by accelerometry and to determine to what degree their mobility is affected by disease activity.
Methods: A group of 50 RA patients, without lower limb clinical disease, and 50 age- and sex-matched healthy controls were included in this cross-sectional study. PA was assessed by accelerometry and with the International Physical Activity Questionnaire (IPAQ). We performed multiple regression analysis not only to compare PA between groups, but also to explore the relation between RA features, including disease activity and cardiovascular risk parameters, and PA. In a randomized group of 30 RA patients a test-retest study was carried out in order to determine the correlation between variations in disease activity and PA.
Results: The number of minutes of moderate and vigorous activity per day, as evaluated by accelerometry, was significantly lower in RA patients than in healthy controls. In RA patients, accelerometry and IPAQ demonstrated concordance to a moderate degree [quadratic weighed kappa index 0.27 (0.06-0.48), P = 0.02]. HAQ negatively correlated with both IPAQ and accelerometry data. The 28-joint DAS using CRP (DAS28-CRP) was also inversely related with IPAQ. Framingham score and metabolic syndrome were inversely associated with PA in RA patients. Interestingly, variations in PA by accelerometry inversely correlated with changes in RA disease activity (r = -0.42, P = 0.02).
Conclusion: In RA patients, accelerometry is a reliable technique to evaluate PA. This study not only showed that RA patients spend less time doing moderate and vigorous PA than healthy controls, but also PA, as assessed by accelerometry, was sensitive to any changes in disease activity.
Keywords: IPAQ; accelerometry; disability; physical activity; rheumatoid arthritis.