The analysis of data from 2011 through 2017 also found that health care coverage and access improved with implementation of the Affordable Care Act (ACA), but reversed after President Donald Trump and congressional Republicans began working to dismantle it, according to Boston University researchers.
"While we found the ACA isn't unraveling, there are real consequences to some of the policies that have been put in place," said lead author Kevin Griffith, a doctoral candidate in the School of Public Health. "We see that you have these policy changes that are affecting millions of people's ability to get insurance, and millions of people forgoing care because they can't afford it."
For the study, Griffith and his team analyzed federal data on 18- to 64-year-olds. The investigators found that uninsurance rates dropped 7.1 percentage points between 2013 and 2016, then rose 1.2 percentage points during 2017, Trump's first year in office.
Rates of adults who did not seek care due to costs reflected similar trends.
The 2017 reversals had the greatest impact on low-income residents of 14 states that didn't expand Medicaid under the ACA.
In those states, which are mainly in the South, decreases in insurance coverage and health care access were four to five times higher than in states that expanded Medicaid.
The study also found that from 2013 to 2016, the gap in health care access between higher- and lower-income Americans narrowed by about 8.5 percentage points in expansion and nonexpansion states.
But between the fourth quarter of 2016 and the fourth quarter of 2017, that gap widened by 2.6 percentage points in nonexpansion states (a relative increase of 11%). It continued to decrease by another 1 percentage point in expansion states (a relative decrease of 8%).
The study appears in the February issue of the journal Health Affairs.
"Medicaid expansion seemed to be a really great way for states to insulate themselves from some of the damage of these federal policies," Griffith said in a university news release. "For states considering Medicaid expansion, this shows that it's a good way to take care of your residents, even regardless of what's going on in Congress."
He said the reversals revealed by the study are worrisome.
"We had this narrowing of disparities in access and coverage, but that's reversing," Griffith said. "Since 2017, the split between white and black, between rich and poor, urban and rural, renters and homeowners -- all of these disparities are getting wider again. That's concerning."