The Effects on Hospital Utilization of the 1966 and 2014 Health Insurance Coverage Expansions in the United States.

Background: Persons with comprehensive health insurance use more hospital care than those who are uninsured or have high-deductible plans. Consequently, analysts generally assume that expanding coverage will increase society-wide use of inpatient services. However, a limited supply of beds might constrain this growth.

Objective: To determine how the implementations of Medicare and Medicaid (1966) and the Patient Protection and Affordable Care Act (ACA) (2014) affected hospital use.

Design: Repeated cross-sectional study.

Setting: Nationally representative surveys.

Participants: Respondents to the National Health Interview Survey (1962 to 1970) and Medical Expenditure Panel Survey (2008 to 2015).

Measurements: Mean hospital discharges and days were measured, both society-wide and among subgroups defined by income, age, and health status. Changes between preexpansion and postexpansion periods were analyzed using multivariable negative binomial regression.

Results: Overall hospital discharges averaged 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 after (adjusted difference, 0.2 discharges [95% CI, -0.1 to 0.4 discharges] per 100 persons; P = 0.26). Hospital days did not change in the first 2 years after implementation but increased later. Effects differed by subpopulation: Adjusted discharges increased by 2.4 (CI, 1.7 to 3.1) per 100 persons among elderly compared with nonelderly persons (P < 0.001) and also increased among those with low incomes compared with high-income populations. For younger and higher-income persons, use decreased. Similarly, after the ACA's implementation, overall hospital use did not change: Society-wide rates of discharge were 9.4 per 100 persons before the ACA and 9.0 per 100 persons after the ACA (adjusted difference, -0.6 discharges [CI, -1.3 to 0.2 discharges] per 100 persons; P = 0.133), and hospital days were also stable. Trends differed for some subgroups, and rates decreased significantly in unadjusted (but not adjusted) analyses among persons reporting good or better health status and increased nonsignificantly among those in worse health.

Limitation: Data sources relied on participant recall, surveys excluded institutionalized persons, and follow-up after the ACA was limited.

Conclusion: Past coverage expansions were associated with little or no change in society-wide hospital use; increases in groups who gained coverage were offset by reductions among others, suggesting that bed supply limited increases in use. Reducing coverage may merely shift care toward wealthier and healthier persons. Conversely, universal coverage is unlikely to cause a surge in hospital use if growth in hospital capacity is carefully constrained.

Primary Funding Source: None.