Impact of Positive Airway Pressure Therapy on Clinical Outcomes in Older Veterans With Chronic Obstructive Pulmonary Disease and Comorbid Obstructive Sleep Apnea (Overlap Syndrome)

Inclusion Criteria: * OSA with moderate-to-severe disease, AHI 20 per hour by in-lab polysomnography with concomitant moderate-severe COPD based on pulmonary function tests (PFTS) and with past significant history (\>10 pack-years) of smoking * Male or female gender * Age greater than or equal to 60 years * Stable treatment regimen for COPD Exclusion Criteria: * Current or prior treatment with PAP or oral appliance * Central sleep apnea defined as central apnea index \>5 per hour and comprising 50% of AHI * Known primary neuromuscular diseases * Disorders that may impact cognitive function including: * neurodegenerative disorders * traumatic brain injury * untreated PTSD and/or history of learning disability * Medicines that may cause or alter sleepiness: sedative hypnotics, or stimulants as these may alter the results * Patient is actively suicidal due to depression, unstable mental health condition * Epworth sleepiness score \>16 (severe sleepiness) or a near-miss or prior automobile accident due to sleepiness within the past 12 months * Narcolepsy is the primary sleep disorder, with requirement of stimulant medications * Employed as a commercial driver or operating heavy machinery * On long-term oxygen therapy prior to start of study, more than 12 hr/day * Patients is unable to use either a nasal or face mask (e.g., facial trauma, claustrophobia) * Consumption of \>3 alcoholic beverages per day or current use of some illicit drugs, as these may contribute to cognitive deficits * Patients who cannot give informed consent * Patients receiving hospice care * Pregnant women due to unknown risks