Study objectives: To develop a short and practical scale (SCOPA-SLEEP) that evaluates nighttime sleep and daytime sleepiness. The scale is developed for research in Parkinson disease but may be of value for other somatic diseases.
Design: Postal survey including 4 instruments, the SCOPA-SLEEP nighttime sleep (5 items) and daytime sleepiness (6 items), the Pittsburgh Sleep Quality Index, and the Epworth Sleepiness Scale.
Setting: Movement Disorders Center, Department of Neurology, Leiden University Medical Center, Leiden, The Netherlands.
Participants: 143 patients with Parkinson disease and 104 controls.
Interventions: N/A.
Measurements and results: Reliability of the scale was high: internal consistency of the nighttime sleep and daytime sleepiness scales were 0.88 and 0.91, respectively (Cronbach alpha), and test-retest reliabilities were 0.94 and 0.89, respectively (intraclass correlation coefficient). Scale scores differed significantly between patients and controls (P < .001). Construct validity was assessed by correlations with scales that addressed similar constructs. Correlation between the nighttime sleep scale and the Pittsburgh Sleep Quality Index was 0.83 (P < .001), and the correlation between the daytime sleepiness scale and the Epworth Sleepiness Scale was 0.81 (P < .001). Factor analysis revealed 1 factor each for both scales, indicating that the scales measure 1 construct, which justifies the calculation of sumscores. The coefficient of variation of both the nighttime sleep and the daytime sleepiness scale was higher than that of the Pittsburgh Sleep Quality Index and the Epworth Sleepiness Scale, indicating a better ability to detect differences between individuals.
Conclusions: The SCOPA-SLEEP is a reliable and valid instrument for assessing nighttime sleep and daytime sleepiness in patients with Parkinson disease.