This study is an examination of sleep, pain, depression, and physical functioning at baseline and 1-year followup among patients with fibromyalgia syndrome (FMS). Although it is clear that these symptoms are prevalent among FMS patients and that they are related, the direction of the relationship is unclear. We sought to identify and report sleep problems in this population and to examine their relationship to pain, depression, and physical functioning.
Patients diagnosed with fibromyalgia were recruited from a Southern California health maintenance organization and evaluated according to American College of Rheumatology criteria in the research laboratory. Six hundred patients completed the baseline assessment and 492 completed the 1-year assessment. Measures included the Center for Epidemiologic Studies Depression Scale, the McGill Pain Questionnaire, the Pittsburgh Sleep Quality Index, and the Fibromyalgia Impact Questionnaire.
The majority of the sample (96% at baseline and 94.7% at 1 year) scored within the range of problem sleepers. Path analyses examined the impact of baseline values on 1-year values for each of the 4 variables. No variable of interest predicted sleep, sleep predicted pain (beta = 0.13), pain predicted physical functioning (beta = -0.13), and physical functioning predicted depression (beta = -0.10).
These findings highlight the high prevalence of sleep problems in this population and suggest that they play a critical role in exacerbating FMS symptoms. Furthermore, they support limited existing findings that sleep predicts subsequent pain in this population, but also extend the literature, suggesting that sleep may be related to depression through pain and physical functioning.