Insurance may not increase emergency department use across all populations

Health insurance increases utilization. That’s pretty close to accepted as an empirical truism, based on the literature to date. By extension—and supported by evidence, if not conventional wisdom—there’s a belief that having health insurance increases use of the emergency department. A new study from Health Affairs, focusing on young adults, comes to a different conclusion.

The most conclusive evidence we have on ED utilization comes from the Oregon Medicaid study, where individual who obtained coverage through a lottery increased their ED use relative to those who didn’t, despite self-reported access to primary care. That’s corroborated by a recent report from the Colorado Hospital Association, which found a 5.6% increase in emergency room utilization, which was substantially higher than the 1.8% increase observed in non-expansion states.

But the Medicaid population isn’t likely to be representative of the population at large.

That’s where this Health Affairs study comes in. Tina Hernandez-Boussard and coauthors looked at the provision allowing young adult to stay on their parents’ coverage until age 26. There’s generally a consensus that this has increased coverage among young adults—a group that has historically had one of the highest uninsured rates—though experts quarrel about just how many people it’s covered.

While there have been a number of studies examining the impact of the under-26 provision (see Aaron’s post at AcademyHealth for the latest), this is the first to analyze use of the emergency department. The authors used a diff-in-diff model and considered both number of ED visits and whether an individual ever used the ED.

In this study of ED visits in three large and diverse US states, we found that ED use by young adults ages 19–25 expanded by a modest amount after the implementation of the ACA insurance expansion but that ED use by people ages 26–31, who were not included in the ACA expansion, grew faster. Relatively slower growth in use by the younger group is consistent with the view that the ACA decreased ED use in this age group.

Furthermore, we found a minimal relative decrease in the rate at which the younger group ever used the ED, compared to the rate for the older group. When we controlled for patients’ demographic characteristics and compared changes in the two groups between the pre and post periods—that is, before and after the ACA provision was implemented—we estimated relative decreases of 2.1 percent in the number of ED visits and 0.4 percent in the probability of ever using the ED for young adults ages 19–25.

There were demographic differences to note:

[O]ur results indicate that the ACA had a stronger association with ED use among women than among men. This may be of interest given a recent finding of Benjamin Sommers and colleagues: Men had a larger estimated increase in insurance coverage as a result of the ACA provision than women had. Young women in particular are in need of regular preventive care for reproductive and general health issues, including human papillomavirus—which affects approximately half of women ages 20–24.

Blacks and whites had similar relative decreases in ED use. However, Hispanics had smaller decreases overall and in individual states. In particular, our data indicate that the ACA was not associated with the number of ED visits per patient for Hispanics in California and Florida. This is particularly troubling given the large numbers of Hispanics in these states.

The study only uses data from California, New York, and Florida, which would seem to introduce some caveats. The authors say those states were selected based on data availability, state population, and state diversity, but acknowledge that using three states could limit the generalizability of their findings.

Like Medicaid enrollees, young adults with access to dependent coverage aren’t representative of the broader population. By definition, they’re young, probably healthy, and come from a family that enjoys the economic security of health insurance (and has the financial means to keep a dependent on the plan). Since this is an extension of coverage, it also implies a general familiarity with insurance and the health system—higher health literacy than someone who was chronically uninsured. But this study signals that among some populations, insurance might actually (albeit modestly) reduce use of the emergency room.

When we have studies that are conducted well and offer compelling findings, it’s tempting to talk in absolutes. But that’s not how research works.

Adrianna (@onceuponA)

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