Insomnia and sleep apnoea are the two most common sleep disorders, found in 6% and 23–50% of the general population respectively. These disorders also frequently co-occur, with 39–58% of sleep apnoea patients reporting symptoms indicative of co-morbid insomnia. When these disorders co-occur, clinicians are faced with difficult treatment decisions, patients experience the additive detrimental impacts of both disorders, and the effectiveness of discrete treatments for each disorder may be impaired. A common finding is that co-morbid insomnia and sleep apnoea (COMISA) is more difficult to treat than either disorder presenting alone. Co-morbid insomnia reduces the initial acceptance of, and later adherence to, continuous positive airway pressure (CPAP) therapy for obstructive sleep apnoea. This has resulted in recent recommendations that treatment approaches should initially target COMISA patients' insomnia to remove this barrier to CPAP treatment, and improve patient outcomes. However, no randomised controlled trial outcomes investigating this treatment approach currently exist.

The current article aims to review and integrate recent research examining the prevalence, characteristics, and theoretical mechanistic relationships between co-occurring insomnia and OSA, and discuss previous treatment attempts.