States that expand their Medicaid programs under President Barack Obama’s health care law may end up saving thousands of lives, a medical journal report released Wednesday indicates.

Until now, the Medicaid debate has been about budgets and states’ rights. But a statistical study by Harvard researchers in the New England Journal of Medicine found a 6 percent drop in the adult death rate in Arizona, Maine and New York, three states that have recently expanded coverage for low-income residents along the general lines of the federal health care law.

The study found that for every 176 adults covered under expanded Medicaid, one death per year would be prevented.

“Policymakers should be should be aware that major changes in Medicaid — either expansions or reductions in coverage — may have significant effects on the health of vulnerable populations,” wrote the researchers from the Harvard School of Public Health.

Medicaid is a federal-state program for low-income and severely disabled people. It covers about 60 million people in the United States. The new law assigned Medicaid a major role in expanding coverage, accounting for about half the 30 million uninsured people expected to gain insurance as a result of the health overhaul.

But the Supreme Court last month ruled that states have the leeway to reject the law’s Medicaid expansion, which is geared to reach mostly uninsured adults without children and with annual incomes up to about $15,400. As a consequence, the Congressional Budget Office projects 3 million fewer people will gain coverage. Although the CBO still expects most states will expand their programs to some degree, the agency’s nonpartisan analysts project that it may take longer than a decade for some governors and legislatures to decide.

Some governors in Republican-led states, including Texas and Florida, have rejected the Medicaid expansion since the high court’s ruling. Many remain on the fence, awaiting the outcome of the November elections and GOP promises to repeal the law. Although Washington will pay all of the cost of the expansion for the first three years, then scale back to a 90 percent share, Republican governors say Medicaid is already too costly and the Obama administration repeatedly has blocked their efforts to streamline the program.

The New England Journal study seems destined to be swept up immediately into the debate. Critics are certain to point out that its lead author, Dr. Benjamin Sommers, is on temporary assignment from Harvard working in a policy division of the federal Department of Health and Human Services, which is carrying out Obama’s overhaul.

In an interview, Sommers said “HHS does not have anything to do with this paper.” The research was under way before he began serving as an adviser to the department, and no federal money was used in the project, he said. Like other major medical publications, the journal rigorously reviews research prior to publication.

The study’s findings counter a widespread perception that having a Medicaid card is little better than being uninsured. Because Medicaid pays doctors far less than Medicare and private insurance, some experts have questioned it will be able to deliver the care that people need.

The study compared key health statistics in the three states that expanded Medicaid coverage with outcomes in neighboring states that did not, examining five years before the expansion and the five years after.

New York, Maine and Arizona have all expanded eligibility for adults since 2000, with New York’s expansion by far the largest. States that did not expand and were used for the comparison included Pennsylvania (for New York), New Hampshire (for Maine), and Nevada and New Mexico (for Arizona.)

The study is not the gold standard for statistical research because subjects were not selected at random, but Sommers said the researchers cross-checked their results and are confident of the findings.

In addition to the drop in death rates among adults ages 20 to 64, the study found a 21 percent drop in delays getting care blamed on cost barriers.

It’s the second recent study to document the benefits of Medicaid. A study of Oregonians published last year found that those with Medicaid were more far more likely to get regular medical care, including preventive screenings. The subjects of the Oregon study were randomly selected.

“Expanding Medicaid to low-income adults is associated with significant gains in health and survival,” said Sommers.