Frequent Emergency Department Users: A Statewide Comparison Before And After Affordable Care Act Implementation.

Frequent emergency department (ED) use often serves as a marker for poor access to non-ED ambulatory care. Policy makers and providers hoped that by expanding coverage, the Affordable Care Act (ACA) would curtail frequent ED use. We used data from California's Office of Statewide Health Planning and Development to compare the characteristics of frequent ED users among nonelderly adults in California before and after implementation of several major coverage expansion provisions in the ACA. Frequent users-patients with four or more annual ED visits-accounted for 7.9 percent of ED patients before and 8.5 percent after those provisions were implemented, and they were responsible for 30.7 percent of all visits before and 31.6 percent after. However, after controlling for patient-level characteristics, we found that the odds of being a frequent ED user were significantly lower post ACA for Medicaid-insured patients. Uninsured patients were also less likely to be frequent users post ACA, while privately insured patients experienced little change. The largest predictors of frequent ED use included having a diagnosis of a mental health condition or a substance use disorder. Interventions to address frequent ED use must involve Medicaid managed care plans, given that more than two-thirds of frequent ED users post ACA have Medicaid as their primary coverage source.