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Objective. To evaluate a multidimensional model testing disease activity, mood disturbance, and poor sleep quality as determinants of fatigue in patients with rheumatoid arthritis (RA).
Method. The data of 106 participants were drawn from baseline of a randomized comparative efficacy trial of psychosocial interventions for RA. Sets of reliable and valid measures were used to represent model constructs. Structural equation modeling was used to test the direct effects of disease activity, mood disturbance, and poor sleep quality on fatigue, as well as the indirect effects of disease activity as mediated by mood disturbance and poor sleep quality.
Results. The final model fit the data well, and the specified predictors explained 62% of the variance in fatigue. Higher levels of disease activity, mood disturbance, and poor sleep quality had direct effects on fatigue. Disease activity was indirectly related to fatigue through its effects on mood disturbance, which in turn was related to poor sleep quality. Mood disturbance also indirectly influenced fatigue through poor sleep quality.
Conclusion. Our findings confirmed the importance of a multidimensional framework in evaluating the contribution of disease activity, mood disturbance, and sleep quality to fatigue in RA using a structural equation approach. Mood disturbance and poor sleep quality played major roles in explaining fatigue along with patient-reported disease activity.
Supported by AR R01-049840 from the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health (P.M. Nicassio). Also supported in part by T32-MH19925, HL 079955, AG034588, AG026364, CA119159, DA 027558, RR00827, P30-AG028748, General Clinical Research Centers Program, the UCLA Cousins Center at the Semel Institute for Neurosciences, and the UCLA Older Americans Independence Center Inflammatory Biology Core.
- Accepted for publication March 23, 2012.