Objective functional mobility and functional disability in patients with rheumatoid arthritis: a cross-sectional study

Background: Rheumatoid arthritis (RA) is linked to ongoing inflammation, disability and reduced physical performance. Conventional measures of disease activity may not properly reflect patients realized functional capacity. The goal of this study was to explore whether objective functional mobility adds information on functional disability beyond inflammatory disease activity. Methods: A cross-sectional study involving 382 RA patients. Disease activity, functional disability and mobility were assessed using DAS28-ESR, HAQ-DI and 8-foot up-and-go test. Spearman’s rank correlation and multiple linear regression were used to evaluate relationships between the variables and the independent association of functional mobility with HAQ-DI after adjustment for disease activity. Results: The mean age was 51.99±8.48 years with females comprising 91.6%. Participants of 61-70 years had significantly higher disability, disease activity and poorer functional mobility then younger group (p=0.036, <0.001 and 0.025 respectively). HAQ-DI correlated strongly with 8-foot up-and-go time (ρ=0.877, p<0.001), but weak correlation with DAS28-ESR (p=0.235 and p<0.001). The regression model explained 78.4% of the variance of HAQ-DI (R2=0.784; adjusted R2=0.783). 8-foot up-go was independently associated with HAQ-DI (t=35.94, p<0.001), whereas DAS-28 ESR was not (p=0.078). Conclusions: Objective functional mobility was more strongly associated with functional disability than inflammatory disease activity and independently associated with HAQ-DI. Adding performance-based assessment of mobility to disease-activity and patient-reported measures may provide a more comprehensive functional assessment of RA and help guide rehabilitation planning.