Association Between the ACA Medicaid Expansions and Primary Care and Emergency Department Use During the First 3 Years.

Background: Evidence is limited and mixed as to how the Patient Protection and Affordable Care Act (ACA) Medicaid expansions affected the utilization of primary care physicians (PCPs) and emergency departments (EDs) at the national level.

Objective: To examine the association between the ACA Medicaid expansions and changes in the utilization of PCP and ED visits at the national level during the first 3 years (2014-2016) of the implementation.

Design: A difference-in-differences analysis to compare outcomes between individuals in 32 states that expanded Medicaid versus individuals in 19 non-expansion states.

Participants: A nationally representative sample of US-born individuals 26-64 years old with family incomes lower than 138% of the federal poverty level from the 2010-2016 Medical Expenditure Panel Survey.

Intervention: ACA Medicaid expansions MAIN MEASURES: We examined PCP-related outcomes ((i) whether a participant had any PCP visit during a year and (ii) the annual number of PCP visits per person) and ED-related outcomes ((i) whether a participant had any ED visit during a year and (ii) the annual number of ED visits per person).

Key Results: A total of 17,803 participants were included in our analysis. We found that the proportion of individuals with any PCP visit during a year marginally increased (difference-in-differences estimate, + 3.6 percentage points [pp]; 95% CI, - 0.4 pp to + 7.6 pp; P = 0.08) following the Medicaid expansions, without any change in the annual number of PCP visits per person. We found no evidence that ED utilization (both the proportion of individuals with any ED visit during a year and the annual number of ED visits per person) changed meaningfully after the Medicaid expansions.

Conclusion: Using the nationally representative data of individuals who were affected by the ACA, we found that the ACA Medicaid expansions were associated with a modest improvement in access to PCPs without an increase in ED use.