Study objectives: Disturbed sleep is a common complaint in patients with rheumatoid arthritis (RA). The majority of the research investigating relationships between sleep and patient-reported outcomes in RA has focused on pain and depression. Poor sleep may also affect disability, though this association has not been explored in RA. The present study represents a cross-sectional examination of the relationship between sleep quality and functional disability in 162 patients with RA. Depression, pain severity, and fatigue were examined as separate mediators of the relationship between sleep quality and disability.
Methods: The sample had an average age of 58.47 years, and 76% were female. Participants completed the following questionnaires as part of a medication adherence intervention study: Pittsburgh Sleep Quality Index, Beck Depression Inventory-II, Medical Outcomes Study Short Form-36, and the Health Assessment Questionnaire.
Results: Poor sleep quality was significantly correlated with higher levels of depressive symptoms, greater pain severity, increased fatigue, and greater functional disability. Hierarchical regression analyses showed that sleep quality was not associated with functional disability when depression, pain severity, and fatigue were entered into the model. Separate mediation analyses of depression, pain severity, and fatigue revealed that pain severity and fatigue were mediators of the relationship between sleep quality and disability.
Conclusions: Sleep quality has an indirect effect on functional disability through its relationship with pain severity and fatigue. Future research should investigate whether improvements in sleep can reduce disability in patients with RA.
Keywords: Sleep quality; depression; disability; fatigue; pain; rheumatoid arthritis.