The expansion of Medicaid has saved more than 27,000 lives since 2010, according to the most definitive study yet on the program’s health effects.

Poor adults who gained Medicaid coverage after the Affordable Care Act expanded access were 21% less likely to die during a given year than those not enrolled, the research shows. By analyzing federal records on 37 million Americans, two economists found that deaths fell not only among older enrollees but also among those in their 20s and 30s — a group often assumed to have few medical needs.

The findings were published this month in a National Bureau of Economic Research working paper as House Republicans were drafting a plan that could significantly cut Medicaid, which covers 71 million low-income or disabled Americans. The House Energy and Commerce Committee, which oversees the program, approved a suite of policies Wednesday that the Congressional Budget Office estimated would cause millions of people to lose their coverage in the years ahead.

The study’s authors said that the publication timing was coincidental — their research has been in progress for two years — but acknowledged that the findings were especially relevant to the current budget discussions.

The researchers found that, on average, it costs Medicaid $179,000 to save a year of life — similar to the amounts spent on health care interventions like cervical cancer screenings and leukemia treatment. It is less than the combined public and private spending on interventions like safety inspections for cars. Previous research showing that Medicaid can save lives was conducted on a much smaller scale and mostly reflected data on older, sicker populations. The new study involved linking tax, death and Medicaid enrollment records to gather data about nearly every poor person in America.

Convincing evidence

Health economists not involved with the study described the work as the most convincing evidence to date that Medicaid — and health insurance in general — saves lives.

“It’s an important scientific contribution that helps us think about the magnitude of what Medicaid does,” said Amy Finkelstein, a health economist at the Massachusetts Institute of Technology who was not involved in the research.

Sarah Miller, a University of Michigan economist who has studied the health effects of Medicaid, said she was particularly struck by the new findings on younger enrollees, who accounted for 29% of the 27,400 lives saved.

“The benefits are a lot more widespread than we originally thought,” Miller said. “From a cost-benefit point of view, there is a lot more benefit of saving someone who is 25 than 61, not because their life is of lesser value, but because there are a lot more years left of life to live.” In the study, people in their 20s and 30s accounted for almost half of the life years saved.

While the relationship between health and health insurance may seem straightforward — access to medical care should lead to better health outcomes — few rigorous studies have been able to find such a connection.

A 15-year study by the Rand Corp., beginning the 1970s, looked at what happened when privately insured patients had to pay more for using medical care, in the form of higher copayments or deductibles. At the end of the study, the researchers found few health differences between patients who had faced higher costs and those who hadn’t.

Improvements

Finkelstein and other researchers looked to the natural experiment that occurred when Oregon held a lottery for Medicaid enrollment in 2008 (the state could not afford to cover everyone who wanted it). The research showed some mental health improvements after two years among people who had gained Medicaid, but no statistically significant change in physical outcomes.

Both of those studies involved relatively small groups of people, making it hard to measure differences in rare medical events or deaths.

Joseph Newhouse, a health policy professor at Harvard University who led the Rand experiment, said he was excited by the new findings. His sample size was too small to measure meaningful health differences effectively, he said. And, he noted, because of medical advancements in the decades since his study, insurance coverage may be more valuable now than it was then.

“We have things that actually work for a number of cancers now, and we have statins,” he said, referring to cholesterol-lowering drugs that have been shown to reduce the risk of heart attacks. “In other words, medical care is probably now more effective at reducing mortality than it was in the 1970s.”

For decades, poor Americans have been the demographic most likely to lack health insurance. Low-wage jobs seldom offer affordable coverage, and for most of Medicaid’s history, it did not cover low-income adults unless they were pregnant, disabled or had young children. But that started to change in 2014, when Obamacare offered states generous federal funding to expand coverage.