Elsevier

Annals of Emergency Medicine

Volume 70, Issue 2, August 2017, Pages 215-225.e6
Annals of Emergency Medicine

Health policy/original research
Effect of the Affordable Care Act Medicaid Expansion on Emergency Department Visits: Evidence From State-Level Emergency Department Databases

https://doi.org/10.1016/j.annemergmed.2017.03.023Get rights and content

Study objective

We assess whether the expansion of Medicaid under the Patient Protection and Affordable Care Act (ACA) results in changes in emergency department (ED) visits or ED payer mix. We also test whether the size of the change in ED visits depends on the change in the size of the Medicaid population.

Methods

Using all-capture, longitudinal, state data from the Agency for Healthcare Research and Quality’s Fast Stats program, we implemented a difference-in-difference analysis, which compared changes in ED visits per capita and the share of ED visits by payer (Medicaid, uninsured, and private insurance) in 14 states that did and 11 states that did not expand Medicaid in 2014. Analyses controlled for state-level demographic and economic characteristics.

Results

We found that total ED use per 1,000 population increased by 2.5 visits more in Medicaid expansion states than in nonexpansion states after 2014 (95% confidence interval [CI] 1.1 to 3.9). Among the visit types that could be measured, increases in ED visits were largest for injury-related visits and for states with the largest changes in Medicaid enrollment. Compared with nonexpansion states, in expansion states the share of ED visits covered by Medicaid increased 8.8 percentage points (95% CI 5.0 to 12.6), whereas the uninsured share decreased by 5.3 percentage points (95% CI –1.7 to –8.9).

Conclusion

The ACA’s Medicaid expansion has resulted in changes in payer mix. Contrary to other studies of the ACA’s effect on ED visits, our study found that the expansion also increased use of the ED, consistent with polls of emergency physicians.

Introduction

Since its passage in 2010, the Patient Protection and Affordable Care Act (ACA) has reduced the number of uninsured from 49 to 29 million1 through newly created private health insurance markets and an expansion of the Medicaid program. Changes in coverage have coincided with improvements in self-reported measures of access to care and health status, and reduced out-of-pocket medical expenditures.2, 3, 4, 5 These changes in coverage have generally had positive effects on hospitals. In states that expanded Medicaid, hospitals have experienced shifts in payer mix from uninsured to Medicaid,6, 7 leading to reductions in hospital uncompensated care8, 9 and improved financial positions.10

Editor’s Capsule Summary

What is already known on this topic

Relatively little is known about the effect of the expansion of Medicaid under the Patient Protection and Affordable Care Act (ACA) on emergency department (ED) utilization.

What question this study addressed

Changes in ED visit rates and ED payer mix (Medicaid, private insurance, and uninsured) were associated with the introduction of Medicaid expansion under the ACA.

What this study adds to our knowledge

In 14 expansion states and 11 nonexpansion states, ED visit rates per capita increased more in Medicaid expansion states than in nonexpansion states after 2014. Compared with nonexpansion states, in expansion states the proportion of ED visits covered by Medicaid increased, whereas the uninsured share decreased.

How this is relevant to clinical practice

The results of this study are not expected to change clinical practice but inform the discussion of ED utilization under various insurance plans.

In addition to changing payer mix, many experts predicted that the ACA would increase use of medical care, potentially straining the existing supply of health care providers,11 including emergency departments (EDs).12 However, the conclusions of early evidence on the ACA’s Medicaid expansion on use of medical care have been mixed. Evidence from hospital discharge data suggests that inpatient discharges have not increased more in states that have expanded Medicaid over those that did not, but evidence from population-based surveys suggests that inpatient visits increased (S. Nikpay et al, unpublished data, 2016).7 However, early evidence from population-based surveys5 and hospital discharge data from selected hospitals13, 14 and states7, 15 suggests that ED visits have not changed. This finding is surprising because some expected ED visits to increase substantially among patients newly eligible for Medicaid.16 In fact, a recent poll by the American College of Emergency Physicians found that 75% of emergency physicians reported that they experienced an increase in patient volume after 2014, and 56% reported they experienced an increase in Medicaid volume specifically.17

Ex ante, it is not clear how insurance expansions, public or private, should affect total ED visits. One view holds that giving previously uninsured individuals access to primary care will reduce their use of the ED by shifting care to other sites. On the other hand, gaining insurance may simply increase the use of all types of care.18 Research on previous health insurance expansions has produced various results. Studies on the Massachusetts health reform, which closely resembles the ACA in that it included both a Medicaid and private insurance expansion, suggest that the coverage expansion led to a reduction in ED visits by improving access to outpatient care.19, 20, 21 In contrast, the Oregon Health Insurance Experiment, which evaluated the effect of expanding Medicaid to low-income adults, found a positive and sustained effect of Medicaid coverage on ED visits.22, 23 Results from individual states’ Medicaid expansions or contractions show a positive relationship between expansion and ED use as well.24, 25 Provisions of the ACA that went into effect before 2014 also yield different conclusions about the effect of coverage expansion on ED visits. The ACA-mandated expansion of private employer-sponsored dependent coverage to children aged 26 years or younger was associated with a small decrease in ED visits.26, 27, 28 In contrast, a study of California’s early Medicaid expansion in 2011 found that ED visits increased, although the effect was temporary.29

Summarizing the previous literature, Medford-Davis et al16 suggested that the effect on ED visits depends on the type of coverage the patient has. They expected that patients who gain insurance through Medicaid, as opposed to marketplace coverage, should increase use of the ED because there is little cost sharing associated with ED use in Medicaid. However, patients who gain marketplace coverage should use the ED less than before because many marketplace plans have large deductibles and cost-sharing requirements.

Although the ACA’s Medicaid expansion creates one income eligibility level in all states expanding Medicaid, the effect of this change on Medicaid enrollment depends on the state’s preexisting Medicaid income eligibility criteria. The policy led to a much larger increase in insurance coverage in states that had very low income eligibility limits before 2014 compared with those with already generous eligibility. Larger increases in coverage should translate to larger effects on ED visits. Therefore, although a simple comparison of states that did and did not implement the ACA Medicaid expansion is of interest, to properly understand the effect of the Medicaid expansion on ED visits, it is important to account for heterogeneity among expansion states in terms of coverage changes.

The goal of this study was to assess whether changes in Medicaid eligibility after 2014 were associated with changes in ED use and payer mix. To this end, we compared the change in total ED visits and the share of ED visits by payer types directly affected by the ACA (Medicaid, uninsured, and private) between states that did and did not expand Medicaid in 2014. Because we hypothesized that the size of the change in total visits and payer share should depend on the size of the population gaining coverage, we accounted for heterogeneity by separately analyzing the changes in visits for states with large and small increases in Medicaid enrollment between 2013 and 2014.

Section snippets

Study Design

The study used a difference-in-differences design to compare the change between the pre- and postexpansion periods between states that did and did not expand Medicaid in 2014. Our analysis sample included 14 expansion states (Arizona, California, Hawaii, Iowa, Illinois, Kentucky, Maryland, Minnesota, North Dakota, New Jersey, Nevada, New York, Rhode Island, and Vermont) and 11 nonexpansion states (Florida, Georgia, Indiana, Kansas, Missouri, North Carolina, Nebraska, South Carolina, South

Results

Figure 1 presents total annual visits per 1,000 population in Medicaid expansion and nonexpansion states, adjusted for seasonality and weighted by state population in 2014. In the pre-expansion period, expansion states had approximately 10 fewer ED visits per 1,000 population each quarter than nonexpansion states. Total visits declined by approximately 2 visits per 1,000 population per quarter between the beginning of 2012 and the end of 2013 in both groups and then diverged from what

Limitations

Our analysis has several important limitations. First, Fast Stats ED data do not contain information from all 50 states and Washington, DC. Therefore, our sample may not be representative of the effect of the ACA on ED visits in all states. However, the states in our sample constitute nearly 70% of the US population and cover all 4 regions of the United States.

Second, because the Fast Stats data are aggregated to the state level, we could not investigate the effect of the Medicaid expansion on

Discussion

Some researchers predicted that the ACA’s coverage expansions would lead to a large short-run increase in ED visits for Medicaid patients and a small reduction in ED visits for privately insured patients purchasing through state nongroup marketplaces.16 Consistent with these predictions, our results showed that Medicaid visits increased in 2014, particularly in states with the largest increases in Medicaid enrollment. We show that the large degree of variation in Medicaid eligibility criteria

References (52)

  • K. Hempstead et al.

    State Medicaid expansion and changes in hospital volume according to payer

    N Engl J Med

    (2016)
  • Cunningham P, Rudowitz R, Young K, et al. Understanding Medicaid Hospital Payments and the Impact of Recent Policy...
  • D. Dranove et al.

    Uncompensated care decreased at hospitals in Medicaid expansion states but not at hospitals in nonexpansion states

    Health Aff (Millwood)

    (2016)
  • F. Blavin

    Association between the 2014 Medicaid expansion and US hospital finances

    JAMA

    (2016)
  • L. Ku et al.

    The states' next challenge—securing primary care for expanded Medicaid populations

    N Engl J Med

    (2011)
  • M. McClelland et al.

    The Affordable Care Act and emergency care

    Am J Public Health

    (2014)
  • J.M. Pines et al.

    Medicaid expansion in 2014 did not increase emergency department use but did change insurance payer mix

    Health Aff (Millwood)

    (2016)
  • American College of Emergency Physicians. 2015 ACEP Poll: Affordable Care Act Research Results....
  • J.P. Newhouse

    Free for All? Lessons From the RAND Health Insurance Experiment

    (1993)
  • P.B. Smulowitz et al.

    Increased use of the emergency department after health care reform in Massachusetts

    Ann Emerg Med

    (2014)
  • S. Miller

    The impact of the Massachusetts health care reform on health care use among children

    Am Econ Rev

    (2012)
  • A.N. Finkelstein et al.

    Effect of Medicaid coverage on ED use—further evidence from Oregon’s experiment

    N Engl J Med

    (2016)
  • S.L. Taubman et al.

    Medicaid increases emergency-department use: evidence from Oregon's health insurance experiment

    Science

    (2014)
  • T. DeLeire et al.

    Wisconsin experience indicates that expanding public insurance to low-income childless adults has health care impacts

    Health Aff (Millwood)

    (2013)
  • A. Ghosh et al.

    The Effect of Medicaid on Adult Hospitalizations: Evidence From Tennessee’s Medicaid Contraction

    (2015)
  • Y.A. Antwi et al.

    Changes in emergency department use among young adults after the Patient Protection and Affordable Care Act’s dependent coverage provision

    Ann Emerg Med

    (2015)
  • Cited by (124)

    View all citing articles on Scopus

    Please see page 216 for the Editor’s Capsule Summary of this article.

    Supervising editor: David J. Magid, MD, MPH

    Author contributions: SN and SF prepared the analysis data, conceived the study design, analyzed the data, and drafted the article. HL and TB provided advice on the study design and reviewed the article. All authors contributed to article revisions. SN takes responsibility for the paper as a whole.

    All authors attest to meeting the four ICMJE.org authorship criteria: (1) Substantial contributions to the conception or design of the work; or the acquisition, analysis, or interpretation of data for the work; AND (2) Drafting the work or revising it critically for important intellectual content; AND (3) Final approval of the version to be published; AND (4) Agreement to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

    Funding and support: By Annals policy, all authors are required to disclose any and all commercial, financial, and other relationships in any way related to the subject of this article as per ICMJE conflict of interest guidelines (see www.icmje.org). The authors have stated that no such relationships exist.

    Readers: click on the link to go directly to a survey in which you can provide feedback to Annals on this particular article.

    A podcast for this article is available at www.annemergmed.com.

    View full text