Dementia risk in patients with comorbid insomnia and obstructive sleep apnea: a propensity score–matched cohort study

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.