Effect of Long-acting Levodopa on Obstructive Sleep Apnea in Parkinson's Disease

Inclusion Criteria: 1. Diagnosis of idiopathic PD consistent with the UK Brain Bank; 2. Presence of OSA on screening PSG, as defined by an AHI ≥ 15/h (moderate to severe OSA); 3. Stable regimen of anti-PD medication for 4 weeks prior to entry into the study, and no planned change during the study Exclusion Criteria: 1. Other major neurological disorder; 2. Already taking long-acting levodopa (at any time of day); 3. Taking short-acting levodopa at bedtime or during the night; 4. Any contraindication to long-acting levodopa (see below); 5. Severe levodopa induced dyskinesias; 6. Already on or requiring treatment for restless legs syndrome ; 7. Body mass index \>35 kg/m2; 8. Intercurrent upper respiratory tract infection; 9. Other known cause of OSA (e.g. craniofacial malformation); 10. Active treatment of OSA (CPAP, dental appliance or other), unless willing to stop treatment 2 weeks prior to start and during the duration of the study.