Comorbid Insomnia and Obstructive Sleep Apnea: Challenges for Clinical Practice and Research

O bstructive sleep apnea (OSA) and insomnia are often thought of as opposing clinical conditions, specifically in regard to alertness and sleepiness. Hyperarousal processes such as increased whole body and brain metabolism, hypothalamic-pituitary-adrenal axis dysregulation, and elevated heart rate and sympathetic nervous system activation may play a key role in the pathophysiology of insomnia, thus causing an elevated level of alertness during both the night and daytime. 1,2 On the other hand, frequent arousals and fragmented sleep associated with OSA often lead to excessive daytime sleepiness, although daytime sleepiness is not universally present in all patients with OSA. METHODS We conducted an extensive MEDLINE search for Englishlanguage studies examining the prevalence of comorbid insomnia and OSA or sleep disordered breathing (SDB), treatment studies of OSA in participants with insomnia, and treatment studies using hypnotics in participants with OSA or SDB. In addition, we searched the reference lists of all identified relevant publications. The keywords used to search for articles on the prevalence of comorbid insomnia and OSA or SDB were insomnia, sleep apnea, and sleep disordered breathing. The search terms used to identify treatment studies of OSA or SDB in patients with insomnia were insomnia, sleep apnea, sleep disordered breathing, positive airway pressure, oral appliance, and surgery. For articles on hypnotic use in patients with OSA or SDB, the search terms used were sleep apnea, sleep disordered breathing, hypnotic, trazodone, amitriptyline, and flurazepam, quazepam, estazolam, temazepam, triazolam (Food and Drug Administration-approved benzodiazepine agents), as well as eszopiclone, zolpidem, and zaleplon (Food and Drug Administration-approved nonbenzodiazepine agents). Studies were included in the review if they reported data from an original study (i.e., no review articles) and reported (a) the prevalence of insomnia assessed via polysomnography, interview, or questionnaires in participants diagnosed with OSA Study Objectives: To review studies examining the cooccurrence of insomnia and obstructive sleep apnea (OSA), explore evidence for the effect of OSA therapy on insomnia symptoms and the effect of insomnia treatments on breathing and sleep in patients with OSA, and discuss challenges in the evaluation and treatment of comorbid insomnia and OSA. Methods/Results: Seven pertinent studies were identified that assessed the prevalence of comorbid insomnia and OSA or sleep disordered breathing. Four studies were identified that examined the effects of OSA treatment in patients with insomnia, and 8 studies were found that examined hypnotic use in patients with OSA or sleep disordered breathing. A high prevalence (39%-58%) of insomnia symptoms have been reported in patients with OSA, and between 29% and 67% of patients with insomnia have an apnea-hypopnea index of greater than 5. Combination therapy, including both cognitive behavior therapy and OSA treatment, resulted in greater improvements in insomnia than did either cognitive behavior therapy or OSA treatment alone. The use of GABAergic nonbenzodiazepine agents has been associated with improvements in sleep and has little to no effect on the apnea-hypopnea index in patients with OSA. Conclusions: Insomnia and OSA frequently cooccur. The optimal strategy for adequately treating comorbid insomnia and OSA remains unclear. Future research examining the impact of insomnia on continuous positive airway pressure therapy is needed. Given the substantial overlap in symptoms between insomnia and OSA, evaluation and treatment of these 2 conditions can be challenging and will require multidisciplinary collaboration among sleep specialists