Though Medicaid expansion has helped to improve insurance coverage for immigrant populations in the United States, uninsurance rates still remain high for those in the U.S. who are not yet citizens, according to a new study by Drexel University and University of Nebraska Medical Center researchers published Monday in the October issue of Health Affairs.

A key provision of the Affordable Care Act (ACA) was that states could choose to expand Medicaid eligibility — to nearly every adult under 138 percent of the federal poverty level — in 2014. To date, 33 states have expanded Medicaid, and 18 states have not.

Prior research has shown that access to health care for immigrants is shaped by federal law and variations in state eligibility for Medicaid, often resulting in disparities in access to care. Researchers at Drexel’s Dornsife School of Public Health and the College of Public Health at the University of Nebraska Medical Center were interested in finding out how state variation in the adoption of Medicaid expansion affected access to health insurance for immigrants compared to U.S. natives.

Using data from the American Community Survey, the researchers identified differences in health insurance coverage between U.S. natives, naturalized citizens and noncitizen immigrants. They found that the percentage of uninsured noncitizens decreased after the ACA went into effect, from 70 percent in 2010 to 54 percent in 2015.

However, when compared to other populations, uninsurance rates for noncitizens remained high, and in fact, the disparity between noncitizens and native citizens grew over the study period. In states that expanded access to Medicaid in 2010, noncitizens had been nearly twice as likely to be uninsured (70 percent vs. 34 percent), compared to 2015, when noncitizens were nearly three times more likely to be uninsured (45 percent vs. just 16 percent).

Study lead author Jim P. Stimpson, PhD, a professor in Drexel’s Dornsife School of Public Health, said the implications are twofold: While the study’s results highlight the great benefits of Medicaid expansion, they also suggest that policymakers must do more to ensure access to health care insurance for noncitizens.

“Even if a policy has an overall beneficial effect, it’s important for policymakers to attend to the differential impact a policy might have on a population,” Stimpson said. “Consequently, for example, the uninsurance rate is roughly double for persons living in non-expansion states compared to persons living in expansion states.”

Currently, immigrants must reside legally in the United States for at least five years to be eligible to receive Medicaid, although some states waive the requirement. Stimpson said that a federal policy that would shorten or eliminate this policy would increase access to care for the more than 44 million immigrants living in the U.S.

“A change in federal policy will have the greatest impact on improving the health insurance rate and reducing disparities in coverage,” Stimpson said. “However, state policies should also be carefully considered, given the significant variation in the adoption of Medicaid expansion and state eligibility requirements.”

Fernando A. Wilson, an associate professor at the University of Nebraska Medical Center’s College of Public Health, co-authored this study.