Early Coverage, Access, Utilization, and Health Effects Associated With the Affordable Care Act Medicaid Expansions: A Quasi-experimental Study

Ann Intern Med. 2016 Jun 21;164(12):795-803. doi: 10.7326/M15-2234. Epub 2016 Apr 19.


Background: In 2014, only 26 states and the District of Columbia chose to implement the Patient Protection and Affordable Care Act (ACA) Medicaid expansions for low-income adults.

Objective: To evaluate whether the state Medicaid expansions were associated with changes in insurance coverage, access to and utilization of health care, and self-reported health.

Design: Comparison of outcomes before and after the expansions in states that did and did not expand Medicaid.

Setting: United States.

Participants: Citizens aged 19 to 64 years with family incomes below 138% of the federal poverty level in the 2010 to 2014 National Health Interview Surveys.

Measurements: Health insurance coverage (private, Medicaid, or none); improvements in coverage over the previous year; visits to physicians in general practice and specialists; hospitalizations and emergency department visits; skipped or delayed medical care; usual source of care; diagnoses of diabetes, high cholesterol, and hypertension; self-reported health; and depression.

Results: In the second half of 2014, adults in expansion states experienced increased health insurance (7.4 percentage points [95% CI, 3.4 to 11.3 percentage points]) and Medicaid (10.5 percentage points [CI, 6.5 to 14.5 percentage points]) coverage and better coverage than 1 year before (7.1 percentage points [CI, 2.7 to 11.5 percentage points]) compared with adults in nonexpansion states. Medicaid expansions were associated with increased visits to physicians in general practice (6.6 percentage points [CI, 1.3 to 12.0 percentage points]), overnight hospital stays (2.4 percentage points [CI, 0.7 to 4.2 percentage points]), and rates of diagnosis of diabetes (5.2 percentage points [CI, 2.4 to 8.1 percentage points]) and high cholesterol (5.7 percentage points [CI, 2.0 to 9.4 percentage points]). Changes in other outcomes were not statistically significant.

Limitation: Observational study may be susceptible to unmeasured confounders; reliance on self-reported data; limited post-ACA time frame provided information on short-term changes only.

Conclusion: The ACA Medicaid expansions were associated with higher rates of insurance coverage, improved quality of coverage, increased utilization of some types of health care, and higher rates of diagnosis of chronic health conditions for low-income adults.

Primary funding source: None.

Publication types

  • Observational Study

MeSH terms

  • Adult
  • Female
  • Health Services / economics
  • Health Services / statistics & numerical data*
  • Health Services Accessibility / legislation & jurisprudence*
  • Health Status*
  • Humans
  • Insurance Coverage / economics
  • Insurance Coverage / legislation & jurisprudence*
  • Male
  • Medicaid / legislation & jurisprudence*
  • Middle Aged
  • Patient Protection and Affordable Care Act*
  • Poverty
  • Self Report
  • United States