RESEARCH PROJECT 3: ABSTRACT Prevalence of obstructive sleep apnea (OSA) among older adults in the US is as high as 56%. Short-term neurological consequences of OSA include cognitive changes such as poor attention and impaired executive function, although the mechanisms for these associations are unclear. OSA also increases risk of Alzheimer’s disease and related dementias (ADRD) and mild cognitive impairment, as well as alters ADRD biomarkers. Positive airway pressure is the gold standard treatment for OSA and improves cognition in clinical trials, including patients with ADRD. Although American Indians have a high prevalence of obesity, a risk factor for both OSA and ADRD, no reliable population-based estimates of OSA prevalence exist for AIs. OSA also is likely underdiagnosed in American Indians, and data strongly suggest a disparity in this modifiable ADRD risk factor. Accordingly, we will generate population-based estimates of OSA prevalence and its association with cognitive function, develop a novel intervention, and conduct a randomized pragmatic trial. For the epidemiology component, we will recruit members of 2 studies affiliated with the Strong Heart Study, the only population-based study of cardiovascular and cerebrovascular disease in American Indians. We will screen 450 cohort members ages 55+ living on 2 Northern Plains reservations for OSA and measure cognitive function. Participants with suspected OSA will undergo testing with the WATCHPAT, an FDA-approved sleep apnea diagnostic device. Participants whose results confirm OSA will be referred for positive airway pressure therapy and be eligible for the trial. Analyses will leverage previously collected data to identify fixed and time- varying risk factors for OSA. Next, we will develop the behavioral intervention by using qualitative methods to revise existing protocols for motivational interviewing and electronic messaging to increase pressure treatment adherence. For the randomized controlled trial, we will recruit 300 American Indians ages 55+ from the same Strong Heart Study communities who receive positive airway pressure treatment for OSA. They will be randomized to receive usual care, or usual care plus the intervention. Data collection at baseline, 3 months and 12 months will include positive airway pressure adherence, sleep quality, cognitive function, and vascular risk factors for ADRD. Primary outcomes are positive airway pressure adherence and cognitive function, with the former evaluated as a mechanistic explanation for change in the latter. Our Specific Aims are to: 1) Estimate the prevalence of OSA and its association with cognitive function in older American Indians, and identify OSA risk factors from existing longitudinal data collected by the 2 Strong Heart-Study-affiliated studies; 2) Develop the behavioral intervention and test its effect on positive airway pressure adherence and sleep quality; and 3) Assess the intervention’s effectiveness on cognitive functio...