title: Increased Emergency Department Use in Illinois After Implementation of the Patient Protection and Affordable Care Act.
abstract: OBJECTIVE
  We examine emergency department (ED) use and hospitalizations through the ED after Patient Protection and Affordable Care Act (ACA) health insurance expansion in Illinois, a Medicaid expansion state.
  
  
  METHODS
  Using statewide hospital administrative data from 2011 through 2015 from 201 nonfederal Illinois hospitals for patients aged 18 to 64 years, mean monthly ED visits were compared before and after ACA implementation by disposition from the ED and primary payer. Visit data were combined with 2010 to 2014 census insurance estimates to compute payer-specific ED visit rates. Interrupted time-series analyses tested changes in ED visit rates and ED hospitalization rates by insurance type after ACA implementation.
  
  
  RESULTS
  Average monthly ED visit volume increased by 14,080 visits (95% confidence interval [CI] 4,670 to 23,489), a 5.7% increase, after ACA implementation. Changes by payer were as follows: uninsured decreased by 24,158 (95% CI -27,037 to -21,279), Medicaid increased by 28,746 (95% CI 23,945 to 33,546), and private insurance increased by 9,966 (95% 6,241 to 13,690). The total monthly ED visit rate increased by 1.8 visits per 1,000 residents (95% CI 0.6 to 3.0). The monthly ED visit rate decreased by 8.7 visit per 1,000 uninsured residents (95% CI -11.1 to -6.3) and increased by 10.2 visit per 1,000 Medicaid beneficiaries (95% CI 4.4 to 16.1) and 1.3 visits per 1,000 privately insured residents (95% CI 0.6 to 1.9). After adjusting for baseline trends and season, these changes remained statistically significant. The total number of hospitalizations through the ED was unchanged.
  
  
  CONCLUSIONS
  ED visits by adults aged 18 to 64 years in Illinois increased after ACA health insurance expansion. The increase in total ED visits was driven by an increase in visits resulting in discharge from the ED. A large post-ACA increase in Medicaid visits and a modest increase in privately insured visits outpaced a large reduction in ED visits by uninsured patients. These changes are larger than can be explained by population changes alone and are significantly different from trends in ED use before ACA implementation.
authors: Department of Emergency Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL; Center for Healthcare Studies, Northwestern University Feinberg School of Medicine, Chicago, IL. Electronic address: s-dresden@northwestern.edu.
authors: Scott M
authors: SM
authors: Dresden
authors: Department of Emergency Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL; Center for Healthcare Studies, Northwestern University Feinberg School of Medicine, Chicago, IL.
authors: Emilie S
authors: ES
authors: Powell
authors: Center for Healthcare Studies, Northwestern University Feinberg School of Medicine, Chicago, IL.
authors: Raymond
authors: R
authors: Kang
authors: Department of Emergency Medicine, Northwestern University Feinberg School of Medicine, Chicago, IL; Center for Healthcare Studies, Northwestern University Feinberg School of Medicine, Chicago, IL.
authors: Megan
authors: M
authors: McHugh
authors: Division of General Internal Medicine and Geriatrics, Northwestern University Feinberg School of Medicine, Chicago, IL.
authors: Andrew J
authors: AJ
authors: Cooper
authors: Division of General Internal Medicine and Geriatrics, Northwestern University Feinberg School of Medicine, Chicago, IL.
authors: Joe
authors: J
authors: Feinglass
mesh_terms: D000293:Adolescent; D000328:Adult; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D007087:Illinois; D007348:Insurance, Health / Q000331:legislation & jurisprudence / Q000706:statistics & numerical data; D065186:Interrupted Time Series Analysis; D008297:Male; D008484:Medicaid / Q000706:statistics & numerical data; D008875:Middle Aged; D058991:Patient Protection and Affordable Care Act / Q000706:statistics & numerical data*; D014481:United States; D055815:Young Adult