“To our knowledge, this is the first study to systematically examine the potential indirect clinical benefits of receiving health care at a non-teaching hospital with greater proximity to one or more AMCs across a wide range of conditions,” said lead author Laura Burke, HMS assistant professor of emergency medicine at Beth Israel Deaconess. “Identifying strategies by which AMCs may enhance care for patients in the entire region has the potential to improve health outcomes for underserved populations.”

In their retrospective cohort study of older Medicare beneficiaries who received care from U.S. acute care hospitals from 2015 to 2017, Burke and colleagues looked at more than 22 million hospitalizations. Nearly 19 million of these, nearly 84 percent, were at community hospitals. They calculated mortality within 30 and 90 days of an inpatient stay. They also calculated patients’ healthy days at home during the follow-up period, defined as the number of days during which the patient was not at an inpatient or long-term facility, outpatient emergency department, or deceased.

Next, the team created four health care market categories. In a market with no AMC presence, no patients were admitted to an AMC. In a market with low AMC presence, up to 20 percent of patients admitted to a hospital were admitted to an AMC. In moderate-presence AMC regions, 20 to 35 percent of patients were admitted to an AMC. And in high-presence AMC markets, more than 35 percent of hospitalized patients were admitted to an AMC.

Burke and colleagues saw stark disparities in the demographic characteristics of the overall populations residing in the four markets, with those with no AMC presence having the lowest median income, lowest mean population, highest mean poverty rate, and highest proportion of white residents. Before accounting for the negative impact poverty and other regional characteristics can have on health, the scientists saw significant association with lower mortality for treatment in markets with high and low AMC presence compared to markets with no AMC presence.

However, when Burke and colleagues adjusted their model for patient characteristics and demographic factors, the association strengthened. Patients hospitalized at community hospitals had lower 30- and 90-day mortality and more healthy days at home at 30 and 90 days when they received care in markets with greater AMC presence.

By contrast, the team found no relationship between market-level AMC presence and outcomes for patients treated at the AMC themselves; that is, the presence of more AMCs in a given market did not affect outcomes for patients of AMCs.

“Taken together these results suggest a spillover effect of AMCs on outcomes for neighboring community hospitals and that the benefits of AMCs for the broader community may be greater than is traditionally recognized,” said Burke, who is an instructor in the Department of Health Policy and Management at the Harvard T. H. Chan School of Public Health.

Burke and colleagues speculate that AMCs may have a positive impact on neighboring community hospitals in a few different ways. Given that physicians tend to practice in close geographic proximity to where they trained, it is possible that the presence of an AMC may lead to a more robust physician supply. Indeed, Burke and colleagues’ analysis revealed that markets with the greatest AMC presence have more nurses and physicians per capita.

Similarly, formal and informal affiliations between AMCs and non-AMCs within the same market may encourage diffusion of knowledge, innovation, as well as sharing best practices and even clinicians, who may work at multiple sites. Perhaps most obviously, patients admitted to community hospitals in regions with greater AMC availability may be more likely to be transferred to a teaching hospital should their conditions warrant tertiary care.

“This study extends prior work examining the role of AMCs in driving acute care outcomes,” said Burke. “The findings are consistent with other studies demonstrating geographic disparities in health care access, and highlights the degree to which rural regions have less access to AMC services. The presence of AMCs may enhance care for patients in rural and remote locations and further research may identify strategies that have the potential to improve health outcomes for underserved populations and widen the reach of the nation’s academic health care institutions.”

Authorship, funding, disclosures

Co-authors included Ryan Burke of Beth Israel Deaconess, E. John Orav of Brigham and Women’s Hospital, Jose Figueroa and Ciara E. Duggan of the Harvard Chan School, and Ashish Jha of Brown University School of Public Health.

This work was supported by a grant from the Association of American Medical Colleges and the National Institutes of Health (R56AG075017).

Burke reported serving as a consultant for the Emergency Medicine Policy Institute outside the submitted work. Figueroa reported receiving grants from Commonwealth Fund, National Institute on Aging, Episcopal Health Foundation, and Arnold Ventures outside the submitted work. This manuscript was written prior to Jha’s government service. The views and opinions expressed are those of the authors and are not made on behalf of the federal government.

Adapted from a Beth Israel Deaconess news release.


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