Background Compared to other clinical groups with chronic pain, people with fibromyalgia syndrome (FMS) report higher levels of fatigue. It is not known whether this is driven by pain, psychological mechanisms or sleep disturbance. This study compared fatigue outcomes in patients with FMS and osteoarthritis (OA). The patients were part of a larger clinical assessment of psychosocial and polysomnographic variables.
Objectives To determine the factors causing fatigue in FMS
Methods 20 recently diagnosed FMS patients (all females; M=40.45, SD=11.21 range 19-58yrs) and 15 patients with OA (all females; M=44.60, SD=11.01 range 19-60yrs) exhibiting localized joint pain and sleep disturbance and were recruited from a single rheumatology unit at Trafford General Hospital, UK. All patients with FM fulfilled the 2010 ACR criteria for the diagnosis, confirmed by an experienced rheumatologist. All patients with OA had radiographic abnormality requiring surgical intervention. All participants completed self-reported sleep scores (Pittsburgh Sleep Quality Index), pain (VAS), fatigue (Fatigue Severity Scale), depression and anxiety measures (Hospital Anxiety and Depression score). All patients had 2 weeks actigraphic assessment of sleep. Multiple regression analysis was conducted with fatigue as the dependent variable and sleep, pain, depression and anxiety measures as predictors. Correlation with fatigue was evaluated compared with actigraphic parameters.
Results The mean fatigue score in FMS was 51±8.40 and 38.27±10.92 in OA. The regression model was significant overall, F(21,10)=4.63, p=0.002, r2=0.54. After controlling for sleep quality, pain severity, pain interference, depression and anxiety, group membership was the only significant predictor of fatigue, B=-7.55, t=-2.40, p=0.026. Fatigue in FMS was correlated with duration of waking after sleep onset and number of awakenings on actigraphy (p=0.034).
Conclusions This data shows that differences in fatigue noted in these two clinical groups are not solely driven by psychological factors. Other factors related to sleep structure may play a larger role in driving these differences. The number and duration of awakenings during sleep contribute to fatigue in FMS but not in OA.
Disclosure of Interest None declared
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