There is no association between the 2 largest healthcare coverage expansions in US history — the implementation of Medicare and Medicaid in July 1966 and the Patient Protection and Affordable Care Act (ACA) in 2014 — and the use of hospital care, according to study results published in Annals of Internal Medicine.

Researchers conducted repeated cross-sectional analyses of the National Health Interview Survey (NHIS) to analyze the 4 years before and 4 years after both the  Medicare expansion in 1966 and the ACA expansion in 2014. For the  ACA expansion, the researchers utilized data from the Medical Expenditure Panel Survey (MEPS) and used files for the 6 years before the implementation (2008 to 2013) and the 2 years after (2014 and 2015). To combine the findings from both eras, data were used from the American Hospital Association (AHA) and the US Census Bureau to calculate hospital use per capita.

Mean hospital discharges and days were estimated overall and for each targeted population before and after each expansion and were defined by income, age, and health status. These estimates were calculated using univariate negative binomial regression. 

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For Medicare expansion, the samples from fiscal years 1963 to 1964 through calendar year 1970 included 407,651 persons in the pre-expansion period and 521,143 in the post-expansion period. Overall, hospital discharges were 12.8 per 100 persons in the 3 years before implementation of Medicare and Medicaid and 12.7 per 100 persons in the 4 years afterward. Hospital days did not change in the first 2 years after implementation but increased afterward. Discharges increased by 2.4 per 100 persons in elderly patients compared with non-elderly patients, as well as in patients with low incomes compared with high-incomes.

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After ACA implementation, overall hospital use did not change. Society-wide rate of discharge was 9.4 per 100 persons before ACA and 9.0 per 100 persons after ACA. Hospital days were also insignificant (48.5 per 100 persons before ACA and 46.0 per 100 persons after ACA). Persons in fair or poor health had a slight increases in discharges and hospital days; people in good or better health had a significant reduction in discharges (0.6 per 100 persons) and hospital days (3.2 per 100 persons).

“In the wake of the 2 largest coverage expansions in US history, neither hospital discharges nor, at least initially, hospital days increased society-wide,” the investigators concluded.


Gaffney A, McCormick D, Bor DH, Goldman A, Woolhandler S, Himmelstein DU. The effects on hospital utilization of the 1966 and 2014 health insurance coverage expansions in the United States [published July 23, 2019]. Ann Intern Med. doi:10.7326/M18-2806