Medicaid Expansion and Preventable Emergency Department Use by Race/Ethnicity.

Introduction: This study aimed to examine changes in emergency department (ED) visits for ambulatory care sensitive conditions (ACSCs) among uninsured or Medicaid-covered Black, Hispanic, and White adults aged 26-64 in the first 5 years of the Affordable Care Act Medicaid expansion.

Methods: Using 2010-2018 inpatient and ED discharge data from nine expansion and five nonexpansion states, an event study difference-in-differences regression model was used to estimate changes in number of annual ACSC ED visits per 100 adults ("ACSC ED rate") associated with the 2014 Medicaid expansion, overall and by race/ethnicity. A secondary outcome was the proportion of ACSC ED visits out of all ED visits ("ACSC ED share"). Analyses were conducted in 2022-2023.

Results: Medicaid expansion was associated with no change in ACSC ED rates among all, Black, Hispanic, or White adults. When excluding California, where most counties expanded Medicaid before 2014, expansion was associated with a decrease in ACSC ED rate among all, Black, Hispanic, and White adults. Expansion was also associated with a decrease in ACSC ED share among all, Black, and White adults. White adults experienced the largest reductions in ACSC ED rate and share.

Conclusions: Medicaid expansion was associated with reductions in ACSC ED rates in some expansion states and reductions in ACSC ED share in all expansion states combined, with some heterogeneity by race/ethnicity. Expansion should be coupled with policy efforts to better link newly insured Black and Hispanic patients to non-ED outpatient care, alongside targeted outreach and expanded primary care capacity, which may reduce disparities in ACSC ED visits.