Sleep disturbances in Japanese patients with Parkinson's disease--comparing with patients in the UK.

Sleep disorders are common in the general population and occur more frequently with advancing age. However, patients with Parkinson's disease (PD) have been known to have various sleep disturbances beyond those to be expected from the effect of aging alone. We tried to quantify the various aspects of nocturnal sleep problems in PD using the PD sleep scale (PDSS). 64 patients with PD and 60 age- and sex-matched controls completed the PDSS. After neurological examinations, we assessed the degree of sleep disorder by the PDSS. We evaluated the severity of PD by the Hoehn and Yahr Scale and the unified PD rating scale (UPDRS). To compare the various aspects of nocturnal sleep problems in PD between in Japan and in the United Kingdom (UK), we referenced and compared our results with those by Chaudhui et al. The PDSS scores in PD group were significantly different from those in controls. Individual items of the scale showed good discriminatory power between PD and controls. Overall tendencies were the same in Japan and in the UK, but there were some different points, especially absence of refreshing quality of sleep in Japan. We believe that the PDSS provides an objective method for targeted therapeutic approaches for the treatment of disturbed sleep in PD even among countries with different cultures, such as Japan and the UK.