Introduction: There is a high prevalence of sleep disorders in Parkinson's disease (PD). AIMS. To assess some basic metric attributes of the SCOPA-Sleep scale, a measure for PD patients; secondary objective: to check the impact caused by the sleep disorder on the health-related quality of life (HRQoL) of patients and their caregivers.
Subjects and methods: 68 PD patients and their main caregivers; measures: Hoehn and Yahr staging, SCOPA-Motor, Clinical Impression of Severity Index (CISI-PD), PDSS, Hospital Anxiety and Depression Scale, SCOPA-Psychosocial, and EuroQoL. Carers filled in a PDSS questionnaire about patient sleep and HRQoL measures (SF-36, EuroQoL). SCOPA-Sleep acceptability, scaling assumptions, internal consistency, construct validity and precision were determined.
Results: SCOPA-Sleep acceptability and scaling assumptions resulted satisfactory, although the nocturnal sleep subescale (SC-Ns) showed a mild ceiling effect (22.1%) and a defective convergent validity was found for daytime sleepiness (SC-Ds) item 6. Internal consistency also was satisfactory for both scales (alpha = 0.84 and 0.75, respectively). The correlation between SC-Ns and PDSS was high (rs = -0.70), as it was between SC-Ns and PDSS questionnaire by caregiver (rs = -0.53). The corresponding coefficients with the SC-Ds gained lower values (rs = -0.41 y -0.50). Standard error of measurement was 1.45 for the SC-Ns and 1.76 for the SC-Ds. Both, patient and caregiver HRQoL showed a loose association with the sleep measures.
Conclusion: SCOPA-Sleep is a feasible, consistent, and useful scale for assessment of sleep disorder in PD patients. A weak association between sleep disorder and HRQoL was found.