Sleep Overlap Syndrome: A Narrative Review

Overlap syndrome, which is known as the coexistence of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnea (OSA), was first defined by Flenley. Although it can refer to concomitant occurrence of any of the pulmonary diseases and OSA, overlap syndrome is commonly considered as the coexistence of OSA and COPD. This disease has unique adverse health consequences distinct from either condition alone. Given the high prevalence of each solitary disease, overlap syndrome is also likely to be common and clinically relevant. Despite the fact that overlap syndrome has been described in the literature for nearly 30 years, paucity of evaluations and studies limited the discussion on diagnosis, prevalence, pathophysiology, treatment, and outcomes of this disease. This review article addresses these issues by reviewing several recent studies conducted in Iran or other countries. This review suggests that overlap syndrome has worse outcomes than either disease alone. Our findings accentuated the urgent need for further studies on overlap syndrome and all overlaps between OSA and chronic pulmonary disease to provide a deeper insight into diagnosis and non-invasive treatments of this disease.