The Parkinson's disease sleep scale: a new instrument for assessing sleep and nocturnal disability in Parkinson's disease

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Abstract
Background: No formal instruments are available for quantifying sleep problems in Parkinson’s disease. Objective: To develop a new sleep scale to quantify the various aspects of nocturnal sleep problems in Parkinson’s disease, which may occur in up to 96% of affected individuals. Methods: Employing a multidisciplinary team approach, a visual analogue scale was devised addressing 15 commonly reported symptoms associated with sleep disturbance in Parkinson’s disease—the Parkinson’s disease sleep scale (PDSS). In all, 143 patients with Parkinson’s disease completed the PDSS, covering the entire spectrum of disease from newly diagnosed to advanced stage. As controls, 137 age healthy matched subjects also completed the scale. Test–retest reliability was assessed in a subgroup of subjects. The Epworth sleepiness scale was also satisfactorily completed by 103 of the patients with Parkinson’s disease. Results: PDSS scores in the Parkinson group were significantly different from the healthy controls. Patients with advanced Parkinson’s disease had impaired scores compared with early/moderate disease. Individual items of the scale showed good discriminatory power between Parkinson’s disease and healthy controls. Relevant items of the PDSS correlated with excessive daytime sleepiness. The scale showed robust test–retest reliability. Conclusions: This appears to be the first description of a simple bedside screening instrument for evaluation of sleep disturbances in Parkinson’s disease. A combination of subitems may help identify specific aspects of sleep disturbance, which in turn may help target treatment.