Residents of these states — concentrated in the Northeast, upper Midwest and West Coast — also have better access to doctors and are less likely to die from preventable illnesses.
Colon cancer deaths in states opposing Medicaid expansion, for example, are an average of 16% higher than in pro-expansion states, according to a Los Angeles Times analysis of state health data.
Deaths from breast cancer are 8% higher on average in anti-expansion states. And adults under 65 are 40% more likely on average to have lost six or more teeth from decay, infection or gum disease.
Medicaid by itself may not close those gaps, which also reflect income and education disparities. And the program's conservative critics, who contend it could ultimately sap state budgets, say poor Americans would be better helped by alternative strategies, including limits on government medical aid to encourage people to take responsibility for their own healthcare.
"Government assistance should not be an entitlement. Government assistance should not be a lifestyle," said Michigan House Speaker Jase Bolger, a Republican who has called for a complete overhaul of the state's Medicaid program, including a four-year limit on benefits for nondisabled adults. "Government assistance should be a temporary hand up. It should be a way to improve people's lives, not trap them in dependency."
Yet most state leaders who are fighting the Medicaid expansion have advanced few alternative plans to tackle their states' health shortfalls. That means that, at least in the short term, America's unhealthiest states could fall even further behind as the Affordable Care Act is implemented.
"Many states may be missing a real opportunity to reduce some of the big differences we see across the country in health," said Cathy Schoen, a health economist at the nonprofit Commonwealth Fund who has studied variations between states.
The architects of the 2010 healthcare law hoped it would help shrink many of these disparities by guaranteeing basic health protections to all Americans no matter where they live.
Medicaid, which is jointly funded by state and federal governments, requires states to cover only certain vulnerable groups, such as poor children and people with disabilities. Some states have expanded their programs while others have not, contributing to wide differences in health coverage.
Today, for example, about 94% of adults under 65 in Massachusetts have health coverage, the highest rate in the nation. The state guarantees coverage through Medicaid or commercial insurance under a plan developed in 2006 by then-Gov. Mitt Romney, a Republican, and Democratic state lawmakers. By contrast, only 68% of working-age Texans are insured, the lowest rate.
Residents of the two states also have vastly different health outcomes. Potentially preventable deaths, a measure of the overall effectiveness of a healthcare system, are 36% higher in Texas than in Massachusetts, according to data from the Centers for Disease Control and Prevention.
The national health law set out two ways to guarantee health coverage.
Americans who make more than the federal poverty level — about $11,500 for an individual — and can't get coverage through their employers will be able to shop for health plans on new Internet-based markets, called exchanges. Government subsidies to offset premiums will be available to consumers making less than four times the poverty level.
Very poor Americans — those who make less than the federal poverty level — were slated to get insurance through a second track: expanded eligibility for Medicaid programs. But last year, that plan was upended when the U.S. Supreme Court ruled that states could elect to forego the Medicaid expansion.
Most GOP governors immediately ruled out enlarging Medicaid and have resisted months of lobbying from doctors, hospitals and business leaders. Republican governors in Florida, Ohio and Michigan who do want to expand Medicaid are being blocked by Republicans in state legislatures.
Many Republicans, citing Medicaid's already ballooning cost, say they are worried the federal government, slated to pick up more than 90% of the tab for the expansion, will renege.
"If history has proven anything, it's that there is no such thing as a temporary entitlement program," South Carolina Gov. Nikki Haley said, thanking state legislators there for rejecting Medicaid growth, which she called a "looming public policy nightmare and fiscal disaster."
So far, 24 states have ruled out expanding Medicaid or appear likely to do so. The District of Columbia and 21 states are on track to expand. It is unclear what will happen in the other five states.
Medicaid has become an increasing burden on state budgets; it is now the largest expense for most states, outpacing education. But growing evidence suggests the program has real health benefits.
Researchers who looked at Maine, New York and Arizona after they expanded Medicaid to poor adults a decade ago found substantial differences between these states and neighboring ones.
Mortality rates declined by 6% in the three expansion states, but remained largely unchanged in the other states. The expansions also decreased the likelihood that residents chose to delay care because of cost and increased the likelihood that they considered themselves in good health, the researchers reported.
"There are important consequences to expanding Medicaid," said Katherine Baicker, a health economist at the Harvard School of Public Health. Baicker, one of the paper's coauthors, served on President George W. Bush's Council of Economic Advisors.
Even a recent study of a Medicaid expansion in Oregon, which found only marginal improvement in cholesterol and blood pressure for Medicaid beneficiaries, highlighted other health improvements, including a dramatic decrease in depression and better reported health.