The overlap syndrome (OS) of chronic obstructive pulmonary disease (COPD) and obstructive sleep apnoea (OSA) is common but often missed in clinical practice. Different clinical COPD phenotypes influence the likelihood of co-existing OSA with the predominant emphysema phenotype being protective whereas the predominant chronic bronchitis phenotype promotes the development of OSA. The management of OS differs from COPD alone, particularly the use of nocturnal positive airway pressure (PAP), and

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... ients with OS not treated with PAP have a worse prognosis, which underlines the importance of correct diagnosis.