The study comes a month after a major U.S. Supreme Court decision ensured that federal subsidies that help most Obamacare customers pay for their health insurance plans are available in every state, and not just in the District of Columbia and the 13 states that are operating their own marketplaces. It also comes slightly more than three months before the start of Obamacare's third open enrollment season on Nov. 1.
In the most recent open enrollment period, ended in February, about 10.2 million were enrolled in private health plans sold on Obamacare exchanges.
Another 12.2 million extra people have been covered by Medicaid and the Children's Health Program since the ACA was implemented.
As of this month, 29 states and the District of Columbia have expanded Medicaid to cover, typically at no charge to enrollees, nearly all adults whose household income is less than 138 percent of the federal poverty level, or $16,242 for a single person in most states. For the first three years of expansion, the federal government is footing 100 percent of the bill for the newly eligible in such states, and then has committed to funding no less than 90 percent of their costs in perpetuity, with states picking up the balance of costs for the newly eligible.
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States that have expanded Medicaid have seen bigger overall reductions in the number of low-income people who lack insurance and personal physicians, and who have difficulty accessing medicine than did the states that did not expand their Medicaid programs, which are jointly run with the federal government, the study found.
States that expanded Medicaid saw the uninsured rate among low-income adults drop by 5.2 percentage points more than non-expansion states, according to the study. Expansion states had drop in the number of such adults who had no personal doctor that was 1.8 percentage points better than non-expansion state, and 2.2 percentage points greater than non-expansion states when measuring the number of low-income earners who had no easy access to medicine.
"As states continue to debate whether to expand Medicaid under the ACA, these results add to the growing body of research indicating that such expansions are associated with significant benefits for low-income populations," the authors of the study wrote.
However, the authors added, "in contrast to prior Medicaid studies, we did not find statistically significant changes in self-reported health."
The ACA, as of 2014, required that most Americans have some sort of health coverage or pay a fine.
To expand coverage, the law mandated that adult children be allowed to stay on their parents' health plan until age 26, authorized the creation of health insurance marketplaces to offer subsidized plans, and authorized states to expand their Medicaid programs to cover, usually at no direct cost to enrollees, nearly all people who earn less than 138 percent of the federal poverty level.