Association of Apathy with Poor Sleep Quality in Patients with Early Parkinson’s Disease

<i>Background and Objectives</i>: Apathy and sleep problems are frequently observed among non-motor symptoms (NMSs) in Parkinson's disease (PD), but the relationship between the two has not been well investigated. This study aimed to determine the extent to which apathy and sleep disturbances are present in people with early PD and whether apathy affects sleep quality. <i>Materials and Methods</i>: Patients diagnosed with early PD, defined as modified Hoehn and Yahr (mHY) stages 1-3 and a disease duration of no more than 5 years, were included in the study. Demographic characteristics were collected, and motor and NMSs including apathy and sleep disturbance were investigated with relevant scales. <i>Results</i>: Of 302 patients with PD, apathy was found in 97 (32.1%) patients. Patients with apathetic PD had significantly less formal education, a more advanced mHY stage, and higher scores on the Unified Parkinson's Disease Rating Scale (UPDRS) part II, total Non-Motor Symptom Scale (NMSS), Beck Depression Inventory (BDI), Apathy Evaluation Scale (AES), and Pittsburgh Sleep Quality Index (PSQI) global scores than patients with non-apathetic PD. The PSQI global score showed significant associations with years of education, UPDRS-II, total NMSS, Mini-Mental State Examination, BDI, and AES scores. For each component of the PSQI, only sleep latency was different between patients with apathetic and non-apathetic PD. Partial correlation analyses for determining the association between apathy and sleep disturbance revealed a significant positive correlation. <i>Conclusions</i>: Apathy is common and associated with poor sleep quality in patients with early PD. These findings suggest that recognizing and addressing apathy may be relevant for managing sleep disturbances in this population.