Dementia Risk in Patients with Comorbid Insomnia and Obstructive Sleep Apnea: A Propensity Score–Matched Cohort Study

Abstract Study Objectives Obstructive sleep apnea (OSA) and insomnia frequently co-occur as comorbid insomnia and sleep apnea (COMISA). While it has increasingly been recognized as a distinct clinical presentation, its cognitive consequences remain unclear. We evaluated the 5-year incident dementia risk associated with COMISA compared with OSA alone. Materials and Methods This retrospective propensity score–matched cohort study using electronic health records from the TriNetX US Collaborative Network. Adults with a first diagnosis of OSA between 2016 and 2019 were followed for up to 5 years. COMISA was defined as an insomnia diagnosis within 90 days of the OSA index date. Patients with COMISA were matched 1:1 to those with OSA alone using propensity scores. Incident all-cause dementia and major dementia subtypes were identified using ICD-10-CM codes. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models. Results After matching, 51 043 patients with COMISA and 51 043 with OSA alone were analyzed. COMISA was associated with an increased risk of all-cause dementia (HR 1·34; 95% CI 1·24–1·46) over 5 year of follow-up. Consistent risk elevations were observed across major dementia subtypes, including vascular dementia (HR 1·35; 95% CI 1·13–1·60), dementia with Lewy bodies (HR 1·85; 95% CI 1·22–2·81), and Alzheimer’s disease (HR 1·19; 95% CI 1·01–1·40). Risk separation became apparent within the first year and remained evident thereafter. Conclusions Among patients with newly diagnosed OSA, comorbid insomnia was associated with a sustained increase in dementia risk. These findings support the clinical relevance of recognizing COMISA as a high-risk clinical presentation in sleep medicine practice.