Nocturnal disturbances and restlessness in Parkinson's disease: using the Japanese version of the Parkinson's disease sleep scale-2.

OBJECTIVE: The aim of this study was to assess the validity and the reliability of the Japanese version of the Parkinson's disease sleep scale (PDSS)-2 and to use this scale to identify nocturnal symptoms and their impact on patient's quality of life.

METHODS: A cross-sectional, case-controlled study was conducted consisting of 93 patients with Parkinson's disease (PD) and 93 age- and gender-matched control subjects. The Japanese version of the PDSS-2 was used for the evaluation of nocturnal disturbances. The patient's quality of life was evaluated with the Parkinson's Disease Quality of Life questionnaire (PDQ-39) and their depressive symptoms were assessed with the Beck Depression Inventory-II (BDI-II), respectively. In addition, the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS) and Parkinson Fatigue Scale (PFS) were administered.

RESULTS: As assessed using the PDSS-2, PD patients had significantly impaired scores compared with control subjects (15.0±9.7 vs. 9.1±6.6, p<0.001). The ESS, BDI-II and PFS scores were significantly impaired in PD patients compared with controls. A satisfactory internal consistency and test-retest reliability score were obtained for the PDSS-2 total score (Cronbach's alpha=0.86). The PDSS-2 was correlated with the PSQI, ESS, BDI-II, PFS, PDQ-39 summary index, all of the PDQ-39 domains and Unified Parkinson's Disease Rating Scale part III. The frequency of restless legs syndrome (RLS) was not significantly different between PD patients and controls (5.5% vs. 2.2%), but nocturnal restlessness was significantly more frequent in PD patients than controls. Stepwise linear regression analyses revealed the PDQ-39 summary index and the PSQI global score as significant predictors for the PDSS-2 total score.

CONCLUSIONS: Our study confirmed the usefulness of the Japanese version of the PDSS-2 that enables the comprehensive assessment of nocturnal disturbances in PD. The association between RLS and nocturnal restlessness in PD requires further study.