Cognitive dysfunction in the aging Veteran population is a growing health concern in the Veterans Health System. It is not known whether OSA coexisting with COPD will enhance the risk for cognitive dysfunction. The investigators sought to investigate whether these two highly prevalent diseases, that often co-exist as the 'Overlap Syndrome', combine to enhance cognitive impairment in the elderly Veteran population. Thus, the investigators will study whether elderly patients with Overlap syndrome have increased cognitive deficits compared with OSA or COPD alone. Additionally, treatment of OSA with positive airway pressure (PAP) has been shown to improve neurocognitive function in moderate-to-severe OSA while cognitive decline in COPD may be reversible through treatment with long-term oxygen therapy. The investigators will also study whether treatment with positive airway pressure (PAP) and supplemental oxygen vs PAP alone will improve cognitive function and improve quality of life of elderly Veterans.

OBJECTIVE: Describe the clinical and physiological characteristics of obstructive sleep apnea (OSA) and comorbid chronic obstructive pulmonary disease (COPD) and study the impact of treatment on neurocognitive outcomes in elderly Veterans.

RESEARCH PLAN: The investigators will study if elderly Veterans with OSA and comorbid COPD have increased neurocognitive deficits and sleepiness with reduced quality of life compared to patients with either OSA or COPD alone (Aim 3) and whether treatment with PAP/NIPPV and supplemental oxygen compared to CPAP alone in elderly Veterans with moderate-to-severe OSA and concomitant moderate-to-severe COPD will improve cognitive function, sleepiness and quality of life (QoL).

Aim A: To determine if elderly Veterans with OSA and comorbid COPD have increased neurocognitive deficits and sleepiness compared to patients with either OSA or COPD.

Hypothesis: Elderly veterans (age 60 years) with moderate-to-severe OSA and concomitant moderate-to-severe COPD will have significantly increased cognitive deficits and daytime sleepiness compared with similar patients with OSA alone or COPD alone.

To study this aim the investigators will prospectively administer and compare the results of a battery of cognitive tests, and sleepiness and QoL questionnaires in elderly patients with OSA, COPD, and the Overlap Syndrome.

Aim B. To determine if treatment with PAP/NIPPV and/or supplemental oxygen compared to CPAP alone in elderly Veterans with OSA and concomitant moderate-to-severe COPD will improve cognitive function, sleepiness, and QoL.

Hypothesis: Therapy with PAP and supplemental oxygen will reverse neurocognitive deficits in one or more domains, reduce sleepiness, and improve QoL compared with CPAP alone in patients with moderate-to-severe OSA and concomitant moderate COPD. This aim will evaluate which specific deficits in neurocognitive function in patients with moderate-to-severe Overlap Syndrome are reversible and most sensitive to the effects of positive airway pressure (PAP) and oxygen vs CPAP alone.

To study this aim the investigators will randomize patients with the Overlap Syndrome to 3months of therapy with PAP and/or oxygen vs CPAP alone for 3 months and evaluate impact on neurocognitive function, sleepiness and quality of life before and after therapy.

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