Nocturnal manifestations of Parkinson's disease (PD) are myriad, have diverse etiologies and include motor, sleep, urinary, and neuropsychiatric symptoms which are often associated with daytime somnolence. While most patients perceive these symptoms as troublesome, the recognition of nocturnal problems related to PD is still low in clinical practice. We conducted a survey using semi-structured interviews and self-rated questionnaires of 215 consecutive patients with PD enrolled in three centers in Thailand to determine the prevalence and risk factors of nocturnal disabilities and their relationship to daytime symptoms. We found that 96.6% of patients reported the presence of nocturnal symptoms as determined by the modified version of Parkinson's Disease Sleep Scale (MPDSS). Our survey indicated that the most frequent and distressing symptom was the interruption of sleep to pass urine (56.7%, 4.4 ± 3.9). The severity of symptoms revealed in the MPDSS increased along with the disease duration (p < 0.05) and Hoehn and Yahr stages (p = 0.01). There were similar to findings of the Nocturnal Akinesia Dystonia and Cramp Score (NADCS) where patients with advanced disease had significantly higher NADCS scores than early/moderate disease (p < 0.001). There was a significant correlation of total MPDSS scores with the total scores of the 9-item Wearing-Off Questionnaire (WOQ-9); (r = -0.43, p < 0.05) [motor (r = -0.35, p < 0.05) and nonmotor subscores (r = -0.43, p < 0.05)]; total nonmotor symptoms (NMS) scores (r = -0.55, p < 0.05); Parkinson's Disease Questionnaire-8 Summary Index (PDQ-8 SI) (r = -0.52, p < 0.05); and the total NADCS (r = -0.35, p < 0.05). Multiple regression analysis identified PDQ-8 SI (β = -0.27, p = 0.005) as the most significant predictor of nocturnal manifestations of PD, followed by the nonmotor subscore of WOQ (β = -0.24, p = 0.006), and the NMS item 20 (feeling light-headed, dizzy, or weak when standing from sitting or lying) (β = -0.22, p = 0.003). Our study found that nocturnal symptoms of PD are very common and we suggest that good clinical practice should include a comprehensive review of nighttime manifestations, particularly for those patients who already experience "wearing-off" symptoms.

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