In this prospective observational study, 67 patients with idiopathic Parkinson’s Disease had polysomnography. Those with moderate to severe OSA were offered CPAP. Subjects were divided into those with or without CPAP and assessed at 6 and 12 months. At 6 months, patients were considered CPAP users if they had used CPAP at home for at least one month. Those who did not use CPAP or declined further treatment were considered non-users. At 12 months, those still using CPAP were considered CPAP users. At 6 months, 30 participants were using CPAP and 11 patients were not using CPAP. At 12 months 21 patients were using CPAP. The Unified Parkinson’s Disease Rating Scale part 1 and Parkinson’s Disease Sleep Scale improved from baseline in the CPAP compliant group at 6 and 12 months. The Montreal Cognitive Assessment (MoCA) and Hospital Anxiety and Depression Scale improved at 12 months. The MoCA improved in those with low baseline score and with REM sleep behavior disorder. Mean CPAP use was 3 hrs and 36 minutes at 12 months in CPAP users.