PROJECT SUMMARY/ABSTRACT Latinxs are aging faster than other racial/ethnic group in the US. By 2050, they are projected to be the largest share of the immigrant, older population. As Latinx immigrants age, they experience the fastest decline in health and emerging health disparities, despite having an initial health advantage. Limited access to health insurance and delayed healthcare utilization is a major determinant of health disparities in older age among Latinx immigrants. Research on how health insurance and access shape health disparities among aging Latinxs is limited by (1) confounding between insurance and immigration and socioeconomic characteristics that shape health and (2) simultaneous changes in insurance access and lifecourse aging as Latinxs enter older adulthood. To address these challenges, the objective of the proposed study is to leverage a policy intervention in Illinois to study changes in health insurance and healthcare utilization among Latinx older-adults using quasi-experimental methods. In 2020 and 2022, Illinois launched the Health Benefits for Immigrant Seniors (HBIA) and Health Benefits for Immigrant Adults (HBIA) programs which were the first state policies that extended coverage equivalent to full-scope Medicaid to low-income undocumented immigrants and noncitizens ages 42 and older. The proposed study will be the first empirical examination of the HBIA and HBIS programs to study health insurance and healthcare changes among Latinx older adults that have implications for health and aging. Our study aims are: (1) To study changes in (a) emergency department (ED) utilization and hospitalizations among Latinx older adults and (b) uncompensated hospital care, following implementation of HBIA/HBIS.; (2) To study how patient-level social determinants of health (SDOH) shape changes in ED utilization and hospitalizations following the implementation of HBIA/HBIS. We will use Illinois hospital CompData, Medicare Costs data, and zip-code linked American Community Survey to examine changes in outcomes from 2018-2023 using interrupted time series and difference-in-difference analysis. This proposed research leverages a novel policy in a major immigrant state to examine how health insurance shapes healthcare among foreign-born Latinx older adults. The findings would contribute to scholarship on the drivers of health disparities among the growing aging immigrant population, and policy policies to expand health insurance to undocumented and noncitizens excluded from healthcare. Collectively these finds would illuminate processes and policies that shape the health of immigrant Latinxs, a significant segment of the nation’s growing older adult population.