Relationship between Apathy and Subjective Poor Night-time Sleep in de novo, Untreated Parkinson's Disease

Background: Sleep disturbance is one of the most common non-motor symptoms of Parkinson's disease (PD). However, the confounding effects of dopaminergic medication on sleep are a major challenge in understanding the impact of sleep disturbance in PD. We investigated the sleep disturbance and associated clinical features in patients with de novo, untreated PD. Methods: One-hundred-eight patients with de novo, untreated PD were included. Night sleep disturbance was evaluated using the night sleep subscale of the Scales for Outcomes in Parkinson's Disease (SCOPA-Sleep). Depression, anxiety, and apathy were assessed using the Geriatric Depression Scale (GDS), Beck Anxiety Inventory (BAI), and Apathy Evaluation Scale (AES), respectively. Early perfusion and dopamine transporter imaging of F-18 FP-CIT PET/CT were performed together with statistical parametric mapping analysis. Results: The night sleep SCOPA-Sleep subscore was correlated with the AES (p = 0.014), BAI (p = 0.014), and GDS (p = 0.023) scores. Patients with poor night sleep were more apathetic (p = 0.013). Additionally, there was increased perfusion in the left posterior cingulate in patients with sleep disturbance and apathy compared to those with sleep disturbance only. Conclusions: Night sleep disturbance was related to mood disorders, particularly apathy, in patients with de novo, untreated PD.