THURSDAY, Jan. 23, 2020 (HealthDay News) -- The physical and mental health of poor people is less likely to be at risk in Southern U.S. states that expanded their Medicaid programs under Obamacare, a new study finds.

Researchers analyzed data from more than 15,500 low-income adults in 12 Southern states and found that Medicaid expansion under the Affordable Care Act reduced the risk of declines in health, particularly among those with severe mental and physical limitations.

"The effect is sizable and would amount to the worst-ranked Southern state rising about halfway up the rankings in state population health if it expanded Medicaid," said senior author J. Michael McWilliams, a professor of health care policy at Harvard Medical School in Boston.

"Unlike many other studies, we were able to focus on some of the most vulnerable populations who stand to gain the most from insurance coverage," McWilliams added.

Fourteen states have not yet expanded Medicaid. They include nine in the South and two that border the region.

"Our study is the first to consider the pathways through which, and populations for whom, expanded access to Medicaid affects the health trajectory of low-income adults," said lead author John Graves, an associate professor of health policy at Vanderbilt University School of Medicine in Nashville, Tenn.

"It fills an important gap between research that has found little evidence of health effects and other research demonstrating that expanded Medicaid saved lives," Graves said in a Vanderbilt news release.

Researchers said their findings could help inform state-level debates over Medicaid expansion, including whether access to safety net programs are an adequate substitute for health insurance coverage. Among other things, the safety net includes such government aid as housing and food assistance, counseling and job training.

"Our research demonstrates that access to the safety net is an inadequate substitute for coverage, and that non-expanding Southern states could materially improve population health if they accept expansion funds," Graves said.

"Health care policy experts and physicians have suspected this for a while but with our study, we now have the actual evidence showing that non-expanding Southern states could materially improve population health if they accept expansion funds," he added.

The study was published in the January issue of the journal Health Affairs.

More information

The U.S. Centers for Medicare and Medicaid Services has more on Medicaid.