This AHRQ Mentored Research Scientist Career Development Award (K01) for Dr. Eric T. Roberts, an assistant professor of health policy and management at the University of Pittsburgh Graduate School of Public Health, will establish Dr. Roberts as a health economist with expertise in health insurance and health care policy for aging and low-income populations. Research proposed for this K01 award will harness natural experiments created by eligibility thresholds and policy variation within Medicare subsidy programs to rigorously evaluate how these programs affect patients' use of care, access to providers, and health. This project will focus on two subsidy programs for low-income Medicare beneficiaries: the Medicare Savings Programs (MSPs), which are partial Medicaid benefits that defray out-of-pocket costs for physician services and inpatient care, and the Part D Low-Income Subsidy (LIS), which helps to pay for prescription drugs. Using the Health and Retirement Study linked to Medicare and Medicaid claims, Dr. Roberts will examine how discontinuities in subsidy eligibility affect patients' use of care?including medication adherence, physician visits, and hospitalizations?and health status. Dr. Roberts will also examine the relationship between state Medicaid policies?specifically, provider payment rates and rules for recertifying program eligibility?with MSP enrollment and patients' access to care. Evidence generated from this research can guide reforms to increase the benefits of the MSPs and LIS to low-income Medicare beneficiaries and to the Medicare program. This project draws on Dr. Roberts' quantitative training, knowledge of Medicare and Medicaid policy, and prior research on health disparities. This work will extend Dr. Roberts' scholarship into the field of aging while incorporating methods in pharmaceutical health services research. Therefore, for this K01 award, Dr. Roberts will engage in training and career development activities that focus on acquiring expertise in aging and pharmaceutical health services research. Through mentorship from health services researchers and clinical experts, Dr. Roberts will also focus on applying training in these content areas to health policy research. This training plan complements the proposed research and will equip Dr. Roberts to establish an independent research program examining policy innovations to improve care for low-income Medicare beneficiaries, quantifying the clinical and economic impacts of policy reforms for patients, payers, and health systems.