title: Increased use of the emergency department after health care reform in Massachusetts.
abstract: OBJECTIVE
  With implementation of the Patient Protection and Affordable Care Act, 30 million individuals are predicted to gain access to health insurance. The experience in Massachusetts, which implemented a similar reform beginning in 2006, should provide important lessons about the effect of health care reform on emergency department (ED) utilization. Our objective is to understand the extent to which Massachusetts health care reform was associated with changes in ED utilization.
  
  
  METHODS
  We compared changes in ED utilization at the population level for individuals from areas of the state that were affected minimally by health care reform with those from areas that were affected the most, as well as for those younger than 65 years and aged 65 years or older. We used a difference-in-differences identification strategy to compare rates of ED visits in the prereform period, during the reform, and in the postreform period. Because we did not have population-level data on insurance status, we estimated area-level insurance rates by using the percentage of actual visits made during each period by individuals with insurance.
  
  
  RESULTS
  We studied 13.3 million ED visits during 2004 to 2009. Increasing insurance coverage in Massachusetts was associated with increasing use of the ED; these results were consistent across all specifications, including the younger than 65 years versus aged 65 years or older comparison. Depending on the model used, the implementation of health care reform was estimated to result in an increase in ED visits per year of between 0.2% and 1.2% within reform and 0.2% and 2.2% postreform compared with the prereform period.
  
  
  CONCLUSIONS
  The implementation of health care reform in Massachusetts was associated with a small but consistent increase in the use of the ED across the state. Whether this was due to the elimination of financial barriers to seeking care in the ED, a persistent shortage in access to primary care for those with insurance, or some other cause is not entirely clear and will need to be addressed in future research.
authors.affiliation: Department of Emergency Medicine, Beth Israel Deaconess Medical Center, Boston, MA. Electronic address: psmulowi@bidmc.harvard.edu.
authors.forename: Peter B
authors.initials: PB
authors.lastname: Smulowitz
authors.affiliation: Dartmouth Institute for Health Policy and Clinical Practice Geisel School of Medicine at Dartmouth, Hanover, NH.
authors.forename: James
authors.initials: J
authors.lastname: O'Malley
authors.affiliation: Department of Economics, Massachusetts Institute of Technology, Boston, MA.
authors.forename: Xiaowen
authors.initials: X
authors.lastname: Yang
authors.affiliation: Division of General Medicine and Primary Care, Beth Israel Deaconess Medical Center, Boston, MA; Department of Health Care Policy, Harvard Medical School, Boston, MA.
authors.forename: Bruce E
authors.initials: BE
authors.lastname: Landon
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D018166:Health Care Reform; D006801:Humans; D008297:Male; D008404:Massachusetts; D008875:Middle Aged; D058991:Patient Protection and Affordable Care Act