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How the ACA Impacted Emergency Room Visits

(Volume 9, Issue 9) Medicaid visits increased, uninsured ones decreased, but effects on doctors unknown.

Prior studies have demonstrated that when , specifically Medicaid, they visit the emergency department (ED) more frequently. A recent study in Health Affairs analyzed the effect of the Affordable Care Act’s (ACA) insurance expansion on overall ED volume and payer mix by comparing Medicaid expansion to non-expansion states.



The authors used an adjusted difference-in-differences approach to compare billing data from 156 EDs in 19 Medicaid expansion states to 322 EDs in 17 non-expansion states from 2012 to 2014. In total, this covered over 40 million emergency department visits. The authors found that insurance expansion was not associated with significant changes in but was associated with various changes in payer mix.

These findings differ slightly from prior literature showing increased ED visits among those who gain Medicaid. Potential explanations for the observed differences include: (1) increased access to non-ED ambulatory care as a result of legislated by the ACA; (2) unobserved differences among those newly eligible for Medicaid under the ACA compared to populations historically eligible for Medicaid; and (3) other differences in expansion vs. non-expansion states such as urgent care centers and .

The authors did find a 27.1% increase in Medicaid ED visits, a relative 31.4% decrease in uninsured ED visits, as well as a 6.7% decrease in privately insured ED visits in expansion states compared to non-expansion states.

Decreased privately insured ED visits may be due either to the crowd out of privately insured patients who switched to Medicaid in expansion states or, alternatively, enrollment in private health insurance through exchanges in non-expansion states counteracting the effects in states embracing the ACA.

The overall impact of these changes in payer mix on ED revenue is likely mixed: Medicaid payments typically exceed those of uninsured patients but are far lower than those received from private insurance. Whether the gain from Medicaid exceeds the loss from fewer private coverage visits is difficult to determine based on this study but of utmost importance to providers of emergency services.

commentary by Michelle Lin, MD, MPH, SM


In 2014 twenty-eight states and the District of Columbia had expanded Medicaid eligibility while federal and state-based Marketplaces in every state made subsidized private health insurance available to qualified individuals. As a result, about seventeen million previously uninsured Americans gained health insurance in 2014. Many policy makers had predicted that Medicaid expansion would lead to greatly increased use of hospital emergency departments (EDs). We examined the effect of insurance expansion on ED use in 478 hospitals in 36 states during the first year of expansion (2014). In difference-in-differences analyses, Medicaid expansion increased Medicaid-paid ED visits in those states by 27.1 percent, decreased uninsured visits by 31.4 percent, and decreased privately insured visits by 6.7 percent during the first year of expansion compared to nonexpansion states. Overall, however, total ED visits grew by less than 3 percent in 2014 compared to 2012-13, with no significant difference between expansion and nonexpansion states. Thus, the expansion of Medicaid coverage strongly affected payer mix but did not significantly affect overall ED use, even though more people gained insurance coverage in expansion states than in nonexpansion states. This suggests that expanding Medicaid did not significantly increase or decrease overall ED visit volume. PMID: 27503974  Pines, JM, et al. Health Affairs. 2016; 35 (8): 1480-1486.

Michelle Lin, MD, MPH, SM
About Michelle Lin, MD, MPH, SM

Dr. Michelle Lin is an assistant professor of Emergency Medicine at the Icahn School of Medicine at Mount Sinai. She completed residency at NYU/Bellevue Hospital Center followed by a health policy research fellowship at Brigham and Women's Hospital. She earned undergraduate and graduate degrees at Northwestern and Harvard. Contact: Website | Twitter | More Posts