Changes in emergency department use associated with Medicaid expansion under the Affordable Care Act: A comparison of waiver and traditional expansion states.

Objective: To determine whether changes in emergency department use associated with Medicaid expansions differed between states undergoing waiver and traditional expansions. Methods: Design: This study was a cross-sectional difference-in-difference and event studies of Medicaid Expansion among states that expanded during or after 2014. Setting: We used a nationally representative cross-sectional survey from all 50 United States and the District of Columbia from 2010 to 2016. Participants: Adults aged 19-65 years with incomes <138% of the federal poverty level were included. Main Outcomes and Measures: Main outcomes were self-reported emergency department (ED) utilization in the last 12 months. Results: Individuals in states across all expansion types were not more likely to report any ED use in the previous year (2.8 percentage point increase [0.0-5.5], Conclusions: Three years after expanding Medicaid under the Affordable Care Act, there is little evidence of differences between traditional and waiver expansion states in changes in any ED use or intensive ED use. Future studies should investigate longer term changes in ED use.