Neurocognitive and Health Impact of Sleep Apnea in Elderly Veterans With Comorbid COPD

Inclusion Criteria: * OSA defined by the International classification of Sleep Disorders-322 diagnostic criteria with moderate-to-severe disease, i.e. apnea hypopnea index (AHI) 15\* per hour by polysomnography * Moderate-to-severe COPD defined by GOLD 2 and 3 (Global Obstructive Lung Disease) 23 criteria with FEV1/FVC ratio \<70% and FEV1 \>30% and \<80% of predicted based on PFT done within the past 1 year and a past significant history (10 pack-years) of smoking * Age 60 years * Male or female gender Exclusion Criteria: * Mild COPD * Mild OSA * Overlap Syndrome with mild OSA plus mild COPD * Central sleep apnea defined as central apnea index \>5 per hour * Already on daytime oxygen or nighttime CPAP, NIPPV, oral appliance * Current smokers * Pregnant women * Disorders of hypoventilation due to known neuromuscular or chest wall diseases\*\* * Patients with significant restrictive lung disease on pulmonary function testing * Recent admission for any acute illness within the prior 4 months * Current psychiatric illness requiring sedating medications * Use of hypnotics, anxiolytics, sedating antidepressants, anticonvulsants, sedating antihistamines, stimulants, or other medications likely to affect alertness or daytime functioning for Aim 3/4 * For Aim 3 and 4 only, existing depression as assessed by the PHQ (Patient Health Questionnaire)-9 (score \>10) * History of learning disability * Inability to sign consent * Epworth sleepiness score 18 or a near-miss or prior automobile accident due to sleepiness within the past 12 months * Patients with unstable heart disease, decompensated heart failure, ejection fraction\<45% or uncontrolled arrhythmias * Patients unable to use either a nasal or face mask (e.g., facial trauma) * Consumption of \> 2 alcoholic beverages per day or past history of excessive alcohol use * Current use of illicit drugs * Patients who have problems with vision or dexterity and hence, cannot use CPAP/NIPPV * Life expectancy is less than 6 months