Fatigue is a major concern for individuals with rheumatoid arthritis (RA). However, in order to treat fatigue adequately, its sources need to be identified.
Data were collected during a single home visit (number of participants = 158). All participants had physician-diagnosed RA. Assessments of self-reported sleep quality, depression, physical activity, RA disease activity, muscle strength, functional limitations, and body composition were made. Information on demographics, medications, and smoking was collected. The Fatigue Severity Inventory (FSI; measuring average fatigue over the past 7 days) was used as the primary outcome. Analyses were first conducted to evaluate bivariate relationships with fatigue. Correlations among risk factors were examined. Multivariate analyses identified independent predictors of fatigue.
The mean ± SD age was 59 ± 11 years, the mean ± SD disease duration was 21 ± 13 years, and 85% of subjects were female. The mean ± SD FSI rating was 3.8 ± 2.0 (range 0-10). In multivariate analyses, self-reported disease activity, poor sleep, depression, and obesity were independently associated with fatigue. Physical inactivity was correlated with poor sleep, depression, and obesity. Mediation analyses indicated that physical inactivity had an indirect association with fatigue, mediated by poor sleep, depression, and obesity.
This cross-sectional study suggests that fatigue may not be solely a result of RA disease activity, but may result from a constellation of factors that includes RA disease activity or pain, but also includes inactivity, depression, obesity, and poor sleep. The results suggest new avenues for interventions to improve fatigue in individuals with RA, such as increasing physical activity or addressing depression or obesity.