People with low incomes who live in states that expanded Medicaid got more of the kind of health care that can keep them healthier in the long run, compared with similar people in non-expansion states, a new study finds.

They also received more health care overall, specifically clinic visits. But they didn’t crowd out patients covered by Medicare or private insurance such as from an employer, the study finds. Those groups continued to have clinic visits and receive preventive care at the same rate as before Medicaid expanded.

The findings, made using detailed health care data from two groups of states that made different decisions about expanding coverage under the Affordable Care Act, are published in BMC Health Services Research by a team from the University of Michigan and the University of California Los Angeles.

“Expanding Medicaid not only expanded low income adults’ overall access to health care, but it also specifically expanded access to preventive care that could pay off down the road in better health,” says Aaron Parzuchowski, M.D., M.P.H., M.S., who led the study while he was a National Clinician Scholar at the U-M Institute for Healthcare Policy and Innovation and the VA Ann Arbor Healthcare System. “At the same time, concerns that other patients would receive less care, or more hurried care with less focus on prevention, did not pan out.”

To qualify for Medicaid coverage in an expansion state, a single adult can have an income no higher than about $20,000.

Three of the five states in the study that hadn’t expanded Medicaid at the time of the analysis – Virginia, North Carolina and Georgia – have now done so. But the other two – Florida and Texas – and eight other states still have not. About 3.5 million adults could qualify for coverage if those 10 states expanded the program.

In addition, more than 1.5 million adults and children have lost Medicaid coverage in recent months across the country during the “unwinding” of pandemic-era provisions; most for administrative reasons rather than increased income.

Parzuchowski, who is now a lecturer in internal medicine at Michigan Medicine, U-M’s academic medical center, worked with the UCLA team led by John Mafi, M.D., as well as A. Mark Fendrick, M.D., director of U-M’s Center for Value Based Insurance Design.

In addition to overall trends in care, their study zeroes in on what experts refer to as “high value” care – medications and other treatments that can help prevent or delay costly health problems in adults with clogged heart arteries, heart failure, diabetes, depression or osteoporosis.

The team used data from the National Ambulatory Medical Care Survey, run by the Centers for Disease Control and Prevention, to look at the insurance coverage, health conditions and medical care of 143 million adults living in high population states from 2012 to 2015. They focused on adults’ visits to physician offices and clinics, excluding federally funded safety net clinics.

Medicaid expansion became law in 2014 in eight of the states studied (Arizona, California, Illinois, Massachusetts, New Jersey, New York, Ohio and Washington), giving the researchers two years before the expansion and two years after to look for differences between those states and the five comparison states. They also accounted for changes in each state’s population during the same time period.

As part of the study, the researchers focused only on the kinds of appointments where it would have made sense for the doctor or other provider to prescribe one of the high value medications or treatments based on the patient’s risk factors or health history. They also included visits where providers could have prescribed low value types of care such as opioid pain medicines for back, neck or head pain, or antibiotics for upper respiratory tract infections.

In all, they found that the number of all Medicaid visits, and the number of Medicaid visits by patients who were likely new Medicaid enrollees, both went up in expansion states but not in non-expansion states. Total Medicaid visits went up by 35%, with 16 more per 100 adults living in the state.

The total number of adult visits, and the visits by patients with Medicare or private insurance, did not change significantly in either group of states.

There was also a 19% increase in the likelihood that a clinic visit by a new Medicaid enrollee would include high value care in expansion states. In non-expansion states the likelihood that a visit by a new Medicaid enrollee would include high value care dropped by 24% in the same timeframe.

"Our findings dispel a frequently stated concern that access to clinicians and quality of care would be reduced for people enrolled in other insurance types in states that expanded Medicaid," said Fendrick.

In addition to Parzuchowski and Fendrick, who are members of IHPI, and Mafi, the study’s authors are UCLA’s Carlos Oronce, Rong Guo and Chi-Hong Tseng.

The study was funded by a National Institute on Aging K76 Career Development Award, and by the VA Office of Academic Affiliations and Michigan Medicine

Evaluating the accessibility and value of U.S. ambulatory care among Medicaid expansion states and non-expansion states, 2012–2015, DOI: 10.1186/s12913-023-09696-x