The timing of the analysis is central to its design. Immigration enforcement activity in Los Angeles County began increasing in early 2025 and then expanded significantly in early June 2025, when high-profile federal operations took place in downtown Los Angeles and other communities. Those operations generated widespread public attention and, according to the researchers, created a natural before-and-after window for studying health care utilization. The team examined patient records at three safety-net hospitals—Los Angeles General Medical Center, Harbor-UCLA Medical Center, and Olive View-UCLA Medical Center—during the twelve months before June 2025 and the four months that followed. These hospitals are a key source of care for immigrant communities in the county, which makes them a sensitive barometer for changes in health-seeking behavior among foreign-born residents.

To distinguish foreign-born patients from U.S.-born patients, the researchers relied on a variable that is routinely collected but rarely exploited for research of this kind: patients’ self-reported country of birth, recorded at the point of care. This allowed the team to compare utilization trends across groups defined by place of birth, including patients born in Mexico, patients born in Central or South America, and patients born in Asia, against a U.S.-born comparison group drawn from the same hospitals over the same period. Because all three facilities serve large, diverse patient populations under the same county health system, the design helps control for hospital-level factors that might otherwise confound comparisons, such as changes in staffing, capacity, or billing practices during the study window.

The headline finding concerns the first four weeks after heightened immigration operations began. During that period, emergency department visits by foreign-born patients decreased by more than 20 percent relative to U.S.-born patients. In other words, after adjusting for the comparison group, roughly one in five emergency visits that would have been expected among foreign-born patients did not occur. This kind of relative decline, measured against a concurrent control population, is methodologically meaningful because it accounts for seasonal patterns, general fluctuations in demand, and any county-wide shocks affecting all patients equally. A drop of that magnitude in a matter of weeks suggests a behavioral response to the enforcement environment rather than a gradual shift in underlying health status.

Over time, the disparity partially receded. By October 2025, the gap in emergency department use between foreign-born and U.S.-born patients had narrowed to 10 percent. The researchers interpret this trajectory as consistent with an acute shock to care-seeking behavior that attenuated as the immediate intensity of enforcement operations subsided, though the gap did not disappear entirely. Even at the reduced level, a persistent 10 percent shortfall in visits among foreign-born patients relative to their U.S.-born counterparts represents a substantial volume of foregone care across a hospital system that serves hundreds of thousands of patients annually. The partial rebound also underscores how sensitive utilization data can be to civic conditions, functioning almost as a real-time indicator of community fear.

Perhaps the most clinically consequential finding is what happened among the foreign-born patients who did seek emergency care. Despite making fewer visits overall, they were more likely to be hospitalized once they arrived. Compared with U.S.-born patients, admission rates increased by 4.8 percentage points among Mexican-born patients, by 5.1 percentage points among patients born in Central or South America, and by 2.5 percentage points among those born in Asia. Higher admission rates among a group that is simultaneously visiting the emergency department less often point toward delayed care: conditions that might have been managed with a short emergency visit and outpatient follow-up instead progressed to the point where inpatient admission became necessary.

This combination of fewer visits and higher admission intensity has a well-understood clinical and economic logic. Emergency departments function as a safety valve for conditions ranging from asthma exacerbations to infections and uncontrolled chronic disease. When patients postpone presentation, illnesses that could have been treated early may advance, requiring longer stays, more intensive interventions, and costlier care. The USC team warns that this dynamic could lead to the development of more serious health conditions and higher costs for both patients and the health care system. For safety-net hospitals, which operate under constrained budgets and serve populations with high rates of uninsurance, an influx of more acutely ill patients carries direct financial and operational consequences, from bed capacity to staffing demands.

The study’s implications extend beyond Los Angeles. Public health researchers have long hypothesized that immigration enforcement can produce a chilling effect on health care use, in which fear of encountering authorities at or near medical facilities deters people from seeking care regardless of their own immigration status. The new findings add rigorous, hospital-level evidence to that literature, quantifying both the magnitude and the duration of the effect during a specific enforcement escalation. Because the analysis covers patients born across multiple world regions, it also suggests that the chilling effect was not confined to a single national-origin group, with measurable declines and admission increases spanning Mexican, Central American, South American, and Asian-born patients, though the magnitude of the admission-rate shift varied by group.

Lead author Sarah Axeen, a scholar at the USC Schaeffer Institute for Public Policy & Government Service and an assistant professor at the Keck School of Medicine of USC, summarized the concern in stark terms. Our findings suggest that immigration enforcement may discourage immigrant patients from seeking acute care when they need it, with potentially serious health consequences for patients and economic costs for the health systems that serve them, she said. That framing captures the dual burden the study documents: a public health cost borne by individual patients whose conditions may worsen untreated, and a systemic cost borne by county hospitals that ultimately absorb more complex, more expensive cases when delayed patients finally present.

The research team included, alongside Axeen, Cameron Kaplan, Daniel Cordova, Manuel Pastor, and Todd Schneberk, all of USC; Annie Ro of the University of California, Irvine; and Anna Gorman of the Los Angeles County Department of Health Services. Data for the work were made available by the National Center for Advancing Translational Sciences of the National Institutes of Health under award number UL1TR001855, and the authors note that the content is solely their responsibility. Published October 5, 2026, in JAMA Network Open under the title Emergency Department Visits After Heightened Immigration Enforcement in Los Angeles County, the study arrives at a moment when policymakers, hospital administrators, and public health officials are weighing how enforcement strategy intersects with community health. Its central message is difficult to ignore: the effects of immigration enforcement are visible not only in arrest statistics and court dockets, but in the quiet, measurable absence of patients from emergency rooms—and in the greater severity of the illnesses they carry when they return.

Subject of Research: The effect of heightened immigration enforcement on emergency department use and hospitalization rates among foreign-born patients at Los Angeles County safety-net hospitals

Article Title: As immigration enforcement increased in L.A., foreign-born patients made fewer ER visits

Article References: As immigration enforcement increased in L.A., foreign-born patients made fewer ER visits. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: immigration enforcement, emergency department visits, foreign-born patients, Los Angeles County, safety-net hospitals, hospitalization rates, JAMA Network Open, health care utilization, chilling effect, public health, USC Schaeffer Center, delayed care