Background In 2014, only 26 states and D.C. chose to implement the Affordable Care Act (ACA) Medicaid expansions for low-income adults. Objective To estimate whether the state Medicaid expansions were associated with changes in insurance coverage, access to and utilization of health care, and self-reported health. Design Comparison of outcomes before and after the expansions in states that did and did not expand Medicaid. Setting U.S. Participants Citizens aged 19–64 with family incomes below 138% of the Federal Poverty Level in the 2010–2014 National Health Interview Surveys. Measurements Health insurance coverage (private, Medicaid, uninsured); health insurance better than last year; visits with doctors in general practice and with specialists; hospitalizations and ED visits; skipped or delayed medical care; usual source of care; diagnoses of diabetes, high cholesterol, and hypertension; self-reported health; and depression. Results In the second half of 2014, low-income adults in expansion states experienced increased health insurance (7.4 percentage points; 95% CI, −11.3 to −3.4) and Medicaid (10.5 percentage points; 95% CI, 6.5 to 14.5) coverage, and increased quality of insurance coverage compared to a year ago (7.1 percentage points; 95% CI, 2.7 to 11.5) when compared to adults in states that did not expand Medicaid. Medicaid expansions were associated with increased visits with doctors in general practice (6.6 percentage points; 95% CI, 1.3 to 12.0), overnight hospital stays (2.4 percentage points; 95% CI, 0.7 to 4.2), and rates of diagnosis of diabetes (5.2 percentage points; 95% CI, 2.4 to 8.1) and high cholesterol (5.7 percentage points; 95% CI, 2.0 to 9.4); changes in other outcomes were not statistically significant. Limitations Observational study may be susceptible to unmeasured confounders; relies on self-reported data; limited post-ACA timeframe provides information on short-term changes only. Conclusions The ACA Medicaid expansions were associated with higher rates of insurance coverage, improved quality of coverage, increased utilization of some types of health care, and higher rates of diagnosis of chronic health conditions for low-income adults.

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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We use large-scale federal survey data linked to administrative death records to investigate the relationship between Medicaid enrollment and mortality. Our analysis compares changes in mortality for near-elderly adults in states with and without Affordable Care Act Medicaid expansions. We identify adults most likely to benefit using survey information on socioeconomic status, citizenship status, and public program participation. We find that, prior to the ACA expansions, mortality rates across expansion and nonexpansion states trended similarly, but beginning in the first year of the policy, there were significant reductions in mortality in states that opted to expand relative to nonexpanders. Individuals in expansion states experienced a 0.132 percentage point decline in annual mortality, a 9.4 percent reduction over the sample mean, as a result of the Medicaid expansions. The effect is driven by a reduction in disease-related deaths and grows over time. A variety of alternative specifications, methods of inference, placebo tests, and sample definitions confirm our main result.