PROJECT SUMMARY/ABSTRACT Six million Americans suffer from atrial fibrillation (AF), a heart rhythm abnormality that contributes to significant morbidity and mortality. By 2050, the number of Americans with AF is expected to double. AF accounts for 15% of ischemic strokes, resulting in permanent disability in 60% of cases and death in up to 20% of cases. Although oral anticoagulation (AC) is effective for AF-related stroke prevention, only 60% of eligible AF patients use AC. This is particularly true among non-white AF patients, for whom AC use is lower and stroke rates are higher. Understanding the barriers that contribute to this gap in AC use and adherence is critical to developing strategies to help decrease AF morbidity and mortality rates in underserved populations. The proposed Diversity Supplement will allow an outstanding early-career investigator to conduct studies in a diverse population of individuals over age 65 with AF to examine the barriers to AC use. This work will be a natural extension of the parent R01 SUPPORT-AF IV: Supporting Use of AC through Provider Prompting about Oral Anticoagulation Therapy for AF. Now in its third year, SUPPORT-AF IV has already established a cohort of diverse individuals and their providers from two distinct health systems in Massachusetts and Florida. The goal of the parent award is to examine the impact of a novel AC clinical decision support tool within the electronic health record (EHR) on AC prescribing behaviors among healthcare providers and clinician engagement with the overarching goal of creating an implementation toolkit. Thus, the candidate will have access to this diverse population to perform vital research while learning essential skills and receiving career guidance from a supportive mentoring team of experts. In Aim 1, the candidate will perform telephone surveys to measure the association of health belief variables (risk perception, trust in providers, beliefs about the effectiveness of AC) + religiosity and spirituality on AC use in older adults with AF on and off AC and established in care at our participating sites. The candidate will then perform a subset analysis to measure the differential association of surveyed variables with AC use in African American and other Black older adults compared with other older adults. For Aim 2, the candidate has developed a rigorous course schedule and career development plan with her mentor to gain expertise in survey research methods, implementation science, community engagement research, mixed methods research, and advanced biostatistics. With her supportive mentoring team and access to UMass Chan’s faculty development programs (e.g., the UMass Chan K-club) this exceptionally promising candidate will receive valuable training, opportunities, and research experiences to launch her independent career.