Clinical phenotype of drug-naïve Parkinson's disease based on nonmotor symptoms

Background: Nonmotor symptoms in Parkinson's disease (PD) are heterogeneous and can result in a variety of symptoms at various disease stages. The objective of the present study was to identify clinically meaningful nonmotor symptoms and to assess the relationship between changes in nonmotor symptoms and cognition and motor symptoms. Methods: A total of 159 patients who had drug-naïve PD participated in this study. Nonmotor symptoms (Nonmotor Symptoms Scale), PD status (Unified Parkinson's Disease Rating Scale), depression (Geriatric Depression Scale or Montgomery-Asberg Depression Scale) and health-related quality of life (39-item Parkinson's Disease Questionnaire) were assessed. An exploratory factor analysis was performed to establish a nonmotor symptom factor, which was analyzed to evaluate whether the results were associated with the clinical severity measures. Results: Exploratory factor analysis revealed one factor comprised of sleep/fatigue, attention/memory and mood/cognition. The modified Hoehn and Yahr Stage, Unified Parkinson's Disease Rating Scale Part III, Montgomery-Asberg Depression Scale and the 39-item Parkinson's Disease Questionnaire Summary Index were independently associated with the sleep/fatigue, attention/memory and mood/cognition domains. The presence of these domains was associated with advanced Parkinson's disease or depressed mood. Conclusions: This study shows that motor impairment and depressed mood in PD are related to sleep/fatigue, attention/memory and mood/cognition. Sleep/fatigue, attention/memory and mood/cognition also had a major impact on health-related quality of life. It is appropriate to identify patients with severe motor symptoms and depressed mood in order to signify the need to consider more detailed care and further assessment.