Association of Sleep Electroencephalography-Based Brain Age Index With Dementia - Data and code

**Importance.** Dementia is an increasing cause of disability and loss of independence in the elderly population yet remains largely underdiagnosed. A biomarker for dementia that can identify individuals with or at risk for developing dementia may help close this diagnostic gap. **Objective.** To investigate the association between a sleep electroencephalography-based Brain Age Index (BAI) -- the difference between chronological age and brain age estimated using the sleep electroencephalogram -- and dementia. **Design, Setting, and Participants.** A retrospective cross-sectional study of 9,834 polysomnograms (5,144 included in BAI examinations) acquired in the Sleep Laboratory at Massachusetts General Hospital from 2009 to 2017. Patients were grouped into dementia, mild cognitive impairment (MCI), symptomatic (cognitive symptoms but no diagnosis of MCI or dementia), nondementia, and healthy individuals using formal inclusion and exclusion criteria, determined by natural language processing applied to the electronic medical record. **Main Outcomes and Measures.** The trend in BAI when moving from healthy through symptomatic to MCI to dementia, and pairwise comparisons of BAI among these groups. **Release.** This project releases the de-identified dataset and analysis code used in the published study, so that the published findings can be independently reproduced from the released inputs and the BAI methodology can be applied to follow-on work. Please consult the published paper for the full results and clinical interpretation.