The United States could have averted about 15,600 deaths if all 50 states expanded Medicaid under the Affordable Care Act, new research suggests.

The Affordable Care Act initially expanded Medicaid, the federal health insurance program for low-income people, to everyone making less than 138 percent of the federal poverty line. But a 2012 Supreme Court ruling weakened the policy, allowing states to reject the expanded program. As of 2019, 36 states and the District of Columbia have adopted the Medicaid expansion, and 14 have not.

Four researchers — University of Michigan economist Sarah Miller, University of California, Los Angeles public health scholar Laura Wherry, National Institutes of Health’s Sean Altekruse and Norman Johnson with the US Census Bureau — used that difference to study what happened to people’s health outcomes in states that expanded the program compared to those that did not. A new working paper published by the National Bureau of Economic Research details their results.

They found that by the fourth year of Medicaid expansion, mortality rates in states that expanded the program were 0.2 percentage points lower than in states that did not.

The study linked data from the American Community Survey between 2008 to 2013 to Social Security Administration, focusing on American citizens between 55 and 64 years old in 2014 who either had less than a high school degree or lived in households with income at or under 138 percent of the federal poverty line.

The researchers found that states that expanded Medicaid saw higher rates of enrollment and lower rates of uninsurance. Among the 55- to 64-year-olds studied, researchers found, receiving Medicaid “reduced the probability of mortality over a 16 month period by about 1.6 percentage points, or a decline of 70 percent.” Based on their findings, they estimate that states’ refusal to expand the program led to 15,600 additional deaths.

This is in line with a growing body of research that shows Medicaid expansion has not only vastly increased access to health insurance, but also improved health outcomes. About 13.6 million adults gained Medicaid coverage under Obamacare.

One 2018 study found Medicaid expansion improved access to surgery and increased the probability that patients seek care before their conditions become complicated. Another 2018 study found Medicaid expansion saved patients with kidney disease starting dialysis. As Sarah Kliff reported for Vox, Medicaid recipients have also report having an easier time paying medical bills and carry less debt.

Miller said the results of this preliminary study are actually conservative. “It’s very likely that younger adults were affected too, or people that were high income in our data, but could have lost a job,” Miller said.

In all, this is yet another piece of data showing that expanding Medicaid has not only improved livelihoods, but actually saved lives.

Medicaid expansion has been very popular. It’s also recently been under threat.

Obamacare was intended to make Medicaid expansion mandatory. But that was challenged in a lawsuit questioning the health care law’s constitutionality. In 2012, the Supreme Court ruled in favor of conservative states. Vox’s Dylan Scott explained the backstory:

On the Supreme Court, Chief Justice John Roberts, according to CNN’s Joan Biskupic, initially ruled that Medicaid expansion could be required, as the ACA originally prescribed. But as he looked for a way to uphold the rest of the law — including the individual mandate, which he initially voted against — Roberts ended up negotiating with the liberal justices, trading the individual mandate for the expansion. The mandate was allowed to stand, and the rest of the law with it, but Medicaid expansion was ruled to be optional. States couldn’t be forced to accept it — and for the past seven years, it has been a major point of debate in statehouses.

That decision has left more than 1 million people without health care coverage.

Medicaid expansion has proven to be incredibly popular. A Kaiser Family Foundation poll found 77 percent of Americans found the policy favorable — including 77 percent of independents and 55 percent of Republicans. Last November, three conservative states, Idaho, Nebraska, and Utah all passed ballot initiatives to expand Medicaid under the Affordable Care Act. Despite the mandate from voters, Republican lawmakers in those states have been trying to roll back Medicaid eligibility.

On the federal level, Republicans spent the majority of their first year with control of Congress and the White House trying to repeal and replace Obamacare with a program that, in every iteration, cut Medicaid. House Republicans passed a bill that phased out Medicaid expansion and ultimately cut the program by $880 billion.

That policy push failed in Congress, but the vision hasn’t changed. Quietly, President Donald Trump’s administration has made it easier for states to restrict access to Medicaid. And Trump’s 2020 budget proposal included Medicaid cuts, including a repeal of Obamacare’s Medicaid expansion. It proposed transforming the current pay-as-needed system to a block grant, where states are given a capped lump-sum fund that wouldn’t grow with increased need or rising costs. The proposed cuts rounded out to about $777 billion, which could leave millions more uninsured.

As the NBER study and others have shown, that could have real life-or-death consequences.