Comorbid Insomnia and Sleep Apnea: From Research to Clinical Practice.

Comorbid insomnia and sleep apnea (COMISA) represents a highly prevalent and clinically significant overlap between the two most common sleep disorders: insomnia and obstructive sleep apnea (OSA). COMISA is associated with greater impairment in sleep, daytime functioning, and physical and mental health compared with insomnia or OSA alone. Despite its prevalence, COMISA has historically been underrecognized, partially due to the conflicting symptoms of insomnia (e.g., hyperarousal and sleeplessness) and OSA (e.g., sleep fragmentation and excessive daytime sleepiness). Recent research highlights that COMISA is not merely the coexistence of insomnia and OSA but may involve unique pathophysiological interactions and clinical phenotypes. This review explores the epidemiology, mechanisms, and clinical manifestations of COMISA. We examine insomnia as a potential extension of OSA, where repeated apneic events lead to conditioned hyperarousal, as well as OSA as an extension of chronic insomnia through mechanisms such as autonomic dysregulation and respiratory instability. Furthermore, we consider COMISA as a distinct entity, characterized by bidirectional interactions between the two conditions that exacerbate their clinical and physiological burden. Key challenges in diagnosing COMISA are discussed, including overlapping symptoms and limitations in current assessment tools. Emerging evidence suggests that COMISA is associated with increased cardiovascular and metabolic risks, greater mental health burden, and reduced treatment adherence to positive airway pressure (PAP) therapy. Advances in tailored therapeutic approaches, including combined cognitive-behavioral therapy for insomnia and OSA management strategies, are highlighted as promising avenues to improve outcomes. Understanding COMISA as a multidimensional condition with diverse phenotypes and mechanisms underscores the need for integrated diagnostic frameworks and personalized treatment strategies to optimize patient care. Further research into its unique features and long-term consequences is critical to advancing clinical practice in sleep and respiratory medicine.