The impact of Medicaid expansion on spending and utilization by older low-income Medicare beneficiaries.

OBJECTIVE: To examine indirect spillover effects of Affordable Care Act (ACA) Medicaid expansions to working-age adults on health care coverage, spending, and utilization by older low-income Medicare beneficiaries.

DATA SOURCES: 2010-2018 Health and Retirement Study survey data linked to annual Medicare beneficiary summary files.

STUDY DESIGN: We estimated individual-level difference-in-differences models of total spending for inpatient, institutional outpatient, physician/professional provider services; inpatient stays, outpatient visits, physician visits; and Medicaid and Part A and B Medicare coverage. We compared changes in outcomes before and after Medicaid expansion in expansion versus nonexpansion states.

DATA COLLECTION/EXTRACTION METHODS: The sample included low-income respondents aged 69 and older with linked Medicare data, enrolled in full-year traditional Medicare, and residing in the community.

PRINCIPAL FINDINGS: ACA Medicaid expansion was associated with a 9.8 percentage point increase in Medicaid coverage (95% CI: 0.020-0.176), a 4.4 percentage point increase in having any institutional outpatient spending (95% CI: 0.005-0.083), and a positive but statistically insignificant 2.4 percentage point change in Part B enrollment (95% CI: -0.003 to 0.050, p = 0.079).

CONCLUSIONS: ACA Medicaid expansion was associated with more institutional outpatient spending among older low-income Medicare beneficiaries. Increased care costs should be weighed against potential benefits from increased realized access to care.