PROJECT SUMMARY/ABSTRACT Alzheimer’s disease (AD) is a major public health burden and disproportionately affects underrepresented populations (URPs), including underrepresented ethnoracial groups and those with low socioeconomic status. URPs are chronically underrepresented in AD clinical research, which has substantial scientific and ethical ramifications. The separate and interacting contributions of sociodemographic and other factors to multiple levels of research participation, including enrollment, retention, and study task completion, are not well understood. Based on current health disparities theoretical frameworks, like the biopsychosociocultural model, multiple factors need to be considered. Therefore, the overall scientific objective of this proposal is to investigate multiple biopsychosocial factors affecting inclusion and participation of URPs in different research settings with a specific focus on ethnoracial and low educational attainment URPs. An innovative approach will be used to examine these important hypotheses by leveraging three existing cohorts from different research settings: (1) the Brain Health Registry (BHR), a cognitive aging-related longitudinal research registry, N>70,000, (2) the Alzheimer’s Disease Initiative (ADNI), an in-clinic observational AD study, N>2,000, and (3) the Health and Retirement Study (HRS), a population-based aging study, N>20,000. The two main hypotheses are (1) Associations between URP status and research participation are affected by multiple biopsychosociocultural factors. We will examine the moderating role of biopsychosociocultural factors on URP research participation in BHR and ADNI; (2) Eligibility criteria of AD trials contribute to underrepresentation of URPs. We will apply a list of current AD trial eligibility criteria to the population-based HRS sample to determine and statistically compare sociodemographic characteristics of eligible/ineligible participants. We will further explore the contributions of trial design characteristics on eligibility. This project is both highly novel and significant as it will be the first to conduct an in-depth examination of multiple biopsychosociocultural factors affecting URP inclusion and participation in a variety of different settings. Improved understanding of the role of biosychosociocultural factors on URP research participation is critical to elucidate sources of research participation disparities frequently affecting URPs. Thus, results are likely to have important public health implications, as this study may inform targeted research inclusion and engagement strategies to improve diversity. This research plan is complemented by a training plan that builds on the candidate’s recent transition from clinical research psychology to the aging and AD field, and therefore includes training in (1) cognitive aging/AD and related clinical trials; (2) complex data sets analysis, advanced biostatistics; (3) AD disparities; (4) URP research participat...