Prevalence and associations of co-morbid insomnia and sleep apnoea in an Australian population-based sample

Introduction: Insomnia and obstructive sleep apnoea (OSA) are the two most prevalent sleep disorders, and frequently co-occur (COMISA) in sleep clinic samples. However, few studies have investigated the prevalence or associations of COMISA in the general population. Methods: We used population-based online survey data from 2044 Australian adults. The prevalence and associations of insomnia, OSA and COMISA were investigated according to symptom-level, and disorder-level definitions. Insomnia was defined according to chronic difficulties initiating and/or maintaining sleep (DIMS; symptom-level), and ICSD-3 chronic insomnia disorder (disorder-level). OSA was defined according to self-reported frequent obstructive events, snoring or doctor-diagnosed OSA (symptom-level), and doctor-diagnosed OSA (disorder-level). COMISA was defined if both conditions were met (for symptom-level, and disorder-level threshold). Associations with other conditions, and general health were investigated with Poisson regression analyses. Results: Chronic insomnia occurred more frequently among participants with doctor-diagnosed OSA (22.3%), compared to those without (14.3%, p = 0.010). Doctor-diagnosed OSA was more common among participants with chronic insomnia (10.2%) compared to those without (6.2%; p = 0.010). DIMS also occurred more frequently among participants with OSA symptoms (66.6%), compared to those without (47.2%; p < 0.001). Participants with symptom-level COMISA reported increased co-morbid conditions, and worse general health compared to participants with symptoms of insomnia-alone, OSA-alone, or neither insomnia/OSA. Conclusions: COMISA at symptom and disorder level were common and associated with increased medical and psychiatric co-morbidity, as well as poor general health. More investigation is required to understand bi-directional associations underpinning the high co-morbidity, and improve diagnostic and treatment approaches for COMISA to reduce associated morbidity.