BACKGROUND: By September 2015, a total of 29 states and Washington, D.C., were participating in Medicaid expansions under the Affordable Care Act. We examined whether Medicaid expansions were associated with changes in insurance coverage, health care use, and health among low-income adults. METHODS: We compared changes in outcomes during the 2 years after implementation of the Medicaid expansion (2014 and 2015) relative to the 4 years before expansion (2010 through 2013) in states with and without expansions, using data from the National Health Interview Survey. The sample consisted of 60,766 U.S. citizens who were 19 to 64 years of age and had incomes below 138% of the federal poverty level. Outcomes included insurance coverage, access to and use of medical care in the past 12 months, and health status as reported by the respondents. RESULTS: A total of 29 states and Washington, D.C., expanded Medicaid by September 1, 2015. In year 2 after implementation, uninsurance rates were reduced in expansion states relative to nonexpansion states (difference-in-differences estimate, -8.2 percentage points; P<0.001) and rates of Medicaid coverage were increased (difference-in-differences estimate, 15.6 percentage points; P<0.001). Expansions were not associated with significant changes in the likelihood of a doctor visit or overnight hospital stay or health status as reported by the respondent. However, as compared with nonexpansion states, expansion states had a decrease in reports of inability to afford needed follow-up care (difference-in-differences estimate, -3.4 percentage points; P = 0.002) and in reports of worry about paying medical bills (difference-in-differences estimate, -7.9 percentage points; P = 0.002) and an increase in reports of medical care being delayed because of wait times for appointments (difference-in-differences estimate, 2.6 percentage points; P = 0.02). CONCLUSIONS: Medicaid expansion was associated with increased insurance coverage and access to care during the second year of implementation, but it was also associated with longer wait times for appointments, which suggests that challenges in access to care persist.
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