title: Impact of Subsidized Health Insurance Coverage on Emergency Department Utilization by Low-income Adults in Massachusetts.
abstract: BACKGROUND
  In 2006, Massachusetts expanded insurance coverage to many low-income individuals.
  
  
  OBJECTIVE
  This study aimed to estimate the change in emergency department (ED) utilization per individual among a cohort who qualified for subsidized health insurance following the Massachusetts health care reform.
  
  
  METHODS
  We obtained Massachusetts public health insurance enrollment data for the fiscal years 2004-2008 and identified 353,515 adults who enrolled in Commonwealth Care, a program that subsidizes insurance for low-income adults. We merged the enrollment data with statewide ED visit claims and created a longitudinal file that indicated each enrollee's ED visits and insurance status each month during the preenrollment and postenrollment periods.
  
  
  METHODS
  We estimated the ratio in an individual's odds of an ED visit during the postperiod versus preperiod by conditional logistic regression.
  
  
  RESULTS
  Among the 112,146 CommCare enrollees who made at least 1 ED visit during the study period, an individual's odds of an ED visit decreased 4% [odds ratio (OR)=0.96; 95% confidence interval (CI), 0.94, 0.98] postenrollment. However, it varied significantly depending on preenrollment insurance status. A person's odds of an ED visit was 12% higher in the postperiod among enrollees not publicly insured prior (OR=1.12; 95% CI, 1.10, 1.25), but was 18% lower among enrollees who transitioned from the Health Safety Net, a program that pays for limited services for low-income individuals (OR=0.82; 95% CI, 0.78, 0.85).
  
  
  CONCLUSIONS
  Expanding subsidized health insurance did not uniformly change ED utilization for all newly insured low-income adults in Massachusetts.
authors.affiliation: Departments of *Emergency Medicine †Health Policy, George Washington University, Washington, DC ‡Department of Biostatistics, Johns Hopkins University, Baltimore, MD §Massachusetts Division of Health Care Finance and Policy, Boston ∥Health Connector Authority, Shrewsbury ¶Health Safety Net, Division of Health Care Finance and Policy, Executive Office of Health and Human Services, Boston, MA #Department of Health Policy, Department of Emergency Medicine, George Washington University, Washington, DC.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Lee
authors.forename: Ru
authors.initials: R
authors.lastname: Ding
authors.forename: Scott L
authors.initials: SL
authors.lastname: Zeger
authors.forename: Aidan
authors.initials: A
authors.lastname: McDermott
authors.forename: Getachew
authors.initials: G
authors.lastname: Habteh-Yimer
authors.forename: Michael
authors.initials: M
authors.lastname: Chin
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Balder
authors.forename: Melissa L
authors.initials: ML
authors.lastname: McCarthy
mesh_terms: D000293:Adolescent; D000328:Adult; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D018166:Health Care Reform / Q000191:economics; D006297:Health Services Accessibility / Q000191:economics; D006801:Humans; D019458:Insurance Coverage / Q000191:economics / Q000706:statistics & numerical data*; D007348:Insurance, Health / Q000191:economics / Q000706:statistics & numerical data*; D008297:Male; D008404:Massachusetts; D008483:Medical Assistance / Q000191:economics / Q000706:statistics & numerical data*; D017057:Medically Uninsured / Q000706:statistics & numerical data; D008875:Middle Aged; D011203:Poverty