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