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

There are no studies regarding the impact of PAP therapy on sleep disturbance, cognitive function and quality of life in patients with OVS. The investigators' rationale is that in patients with moderate-severe OVS, PAP therapy will effectively alleviate sleepiness, sleep disturbances and cognitive deficits, and, thereby, improve QoL. 'PAP' includes either continuous positive airway pressure (CPAP) or noninvasive positive airway pressure ventilation (NIPPV). Objectives: Specifically, the investigators will study the effectiveness of PAP therapy vs. conservative care in reducing daytime sleepiness and in improving sleep quality and QoL in older Veterans with OVS. The investigators will also explore whether CPAP is non-inferior to noninvasive positive airway pressure ventilation (NIPPV) in reducing daytime sleepiness, sleep disturbances and neurocognitive dysfunction, and in improving QoL in older Veterans with OVS.