Sleep and Circadian Rhythm Regulation in Early Parkinson Disease

Importance: Sleep disturbances are recognized as a common nonmotor complaint in Parkinson disease but their etiology is poorly understood. Objective: To define the sleep and circadian phenotype of patients with early-stage Parkinson disease. Design, Setting, and Participants: Initial assessment of sleep characteristics in a large population-representative incident Parkinson disease cohort (N=239) at the University of Cambridge, England, followed by further comprehensive case-control sleep assessments in a subgroup of these patients (n=30) and matched controls (n=15). Main Outcomes and Measures: Sleep diagnoses and sleep architecture based on polysomnography studies, actigraphy assessment, and 24-hour analyses of serum cortisol, melatonin, and peripheral clock gene expression (Bmal1, Per2, and Rev-Erbα). Results: Subjective sleep complaints were present in almost half of newly diagnosed patients and correlated significantly with poorer quality of life. Patients with Parkinson disease exhibited increased sleep latency (P = .04), reduced sleep efficiency (P = .008), and reduced rapid eye movement sleep (P = .02). In addition, there was a sustained elevation of serum cortisol levels, reduced circulating melatonin levels, and altered Bmal1 expression in patients with Parkinson disease compared with controls. Conclusions and Relevance: Sleep dysfunction seen in early Parkinson disease may reflect a more fundamental pathology in the molecular clock underlying circadian rhythms.