Sleep problems and daytime fatigue in a sample of fibromyalgia patients: a preliminary psychometric evaluation of the Scales for Outcomes in Parkinson’s (SCOPA) Sleep Scale

Objective: This study evaluated the psychometric properties of the Scales for Outcomes in Parkinson’s Disease – Sleep Scale (SCOPA-Sleep) in a sample of patients with fibromyalgia syndrome (FMS), and examined the unique and interactive associations between sleep problems, daytime fatigue, and quality of life. Method: A total of 79 adults diagnosed with FMS according to the 2010 American College of Rheumatology criteria completed measures assessing sleep problems, daytime fatigue (SCOPA-Sleep), and health-related quality of life (EuroQOL-5D). Exploratory factor analysis (EFA) and internal consistency analyses assessed the dimensionality and reliability of the SCOPA-Sleep. Multiple linear regression examined confounding and moderation effects of sleep problems and fatigue on quality of life, controlling for sociodemographic variables. Results: EFA supported a two-factor structure of the SCOPA-Sleep reflecting distinct subscales for nighttime sleep problems and daytime fatigue. The subscales were uncorrelated, and both demonstrated strong internal consistency (α = .87 and .84, respectively). Regression analyses revealed that daytime fatigue was not significantly associated with quality of life after adjusting for covariates. However, sleep problems were a significant predictor of reduced quality of life (β = – .33, p < .01). No significant interaction between sleep problems and fatigue was observed. Conclusions: The SCOPA-Sleep may be a useful brief screening tool for sleep-related impairments in clinical FMS assessment. However, given the relatively small and homogeneous sample (predominantly middle-aged women not currently employed), the generalizability of these findings is limited. Future research should replicate these results in larger and more diverse FMS populations.