Adherence Determinants in the Health Electronic Record Evaluation of Statins (ADHERES) - PROJECT SUMMARY Statins are the cornerstone for preventing and treating atherosclerotic cardiovascular disease (ASCVD), the leading cause of death worldwide. Yet even the highest-risk patients face challenges initiating and continuing these low-cost, life-saving medications. Clinicians also fail to prescribe statins when indicated, and health systems may lack the infrastructure to systematically monitor statin adherence. Thus, the objective of the proposed study, Adherence Determinants in the Health Electronic Record Evaluation of Statins (ADHERES), is to determine reasons for statin nonuse across diverse populations as a strategy to reduce health disparities. Specifically, this study will fill the knowledge gap of why certain patient groups (historically marginalized racial and ethnic groups, women, and older adults) are less likely to use statins by leveraging electronic health record (EHR) data and targeted focus groups. Statin use is typically collected in discrete, structured EHR data fields. However, structured EHR data may be incomplete, lack vital information about shared decision-making available around statin use, and fail to capture the variety of reasons for statin nonuse. A better understanding of the patient, clinician, and health system factors associated with statin nonuse thus requires the simultaneous study of structured, unstructured, and patient- generated EHR data from different data sources and patient populations, and ascertaining patient and clinician perspectives through qualitative approaches. To tackle this challenging public health problem, a multidisciplinary team that includes experts in preventive cardiology, health equity research, biomedical informatics, implementation science, community partnerships, and qualitive methods has been assembled. EHR data sources include ~3 million eligible patients from Stanford Health Care, the Veterans Health Administration, and Houston Methodist. Aim 1 will characterize gaps in guideline-directed statin use across diverse patient groups and clinical indications using structured and unstructured EHR data and identify patient profiles and characteristics linked to statin nonuse. Aim 2 will elucidate reasons for statin nonuse in unstructured EHR and patient-generated health data using large language models. Aim 3 will validate and extend these reasons and co-design solutions to improve statin adherence through 10 patient (n=80 participants) and 4 clinician (n=20 participants) focus groups in partnership with the National Minority Health Alliance, a nonprofit organization committed to eliminating health disparities. Findings from ADHERES will be directly actionable in all three health systems by more accurately capturing gaps in guideline-directed statin use, and lead to the implementation of user-centered interventions to address identified barriers. This multi-pronged approach can be scaled beyond statins to improve adherence and the equitable use of other guideline-directed, lifesaving cardiovascular treatments.