Overlap Syndrome of Chronic Obstructive Pulmonary Disease and Obstructive Sleep Apnea: A Two-Faced Janus

Obstructive Sleep Apnoea Syndrome (OSAS) and Chronic Obstructive Pulmonary Disease (COPD) are common respiratory diseases, associated with significant morbidity, worldwide. They frequently co-exist and the overlap syndrome is associated with greater hypoxia and hypercapnia in comparison with COPD or OSAS alone. Unfortunately, the overlap syndrome is still underdiagnosed and undertreated in clinical practice, leading to increased morbidity and mortality. The aim of this review is to present why OSAS is more prevalent among COPD patients, how to differentiate between the common sleep alteration in COPD and the overlap syndrome, the current screening, diagnostic and therapeutic approach of the overlap syndrome.