One of the greatest triumphs the United States has made in medical care is the steady progress in preventing and treating heart disease. It is still the No. 1 cause of death in America. That’s why any step in the wrong direction attracts expert attention. In 2015 heart disease deaths suddenly went up for the first time in more than a decade. Deaths decreased again in 2016, but the broader trend line is troubling: Progress has stalled in recent years after consistent reductions in heart disease mortality since 1969. The worst news in the heart disease data may be that we are heading for two Americas on the country’s leading cause of death.

A new study in the Journal of the American Medical Association-Cardiology shows that while every state cut its burden from cardiovascular disease between 1990 and 2016, measured in lost years of healthy life, the progress is nowhere near even between states. The nationwide progress was attributed to universal and large gains among women, as well as less smoking and the arrival of blockbuster cholesterol-reducing drugs, like Lipitor. But 13 states have lost some of their gains in the last half-dozen years (2010–2016), and nine states saw large increases relative to other states in how much of the heart disease burden they carried over the full 25-year period of the study.

The nine states that have done the worst in the past quarter century share something else in common: All voted for Donald Trump in the 2016 presidential election.

“There’s a lot of interest in economic disparities in the U.S., but the health disparities are a really clear reflection of the social and economic disparities that we know exist,” Professor Greg Roth told CNBC. Roth focuses on global cardiovascular health surveillance, population health and quality of care and outcomes for cardiovascular diseases at the University of Washington School of Medicine. “Where the rubber hits the road is the health risks,’’ he said.

Of the 13 states backtracking between 2010 and 2016 on CVD progress, in both male and female populations, the majority also are red states. The list includes Indiana, West Virginia, Kansas, South Dakota, Idaho, Utah, Kentucky, Missouri, Tennessee, Arkansas and Arizona. (One blue state, New Mexico, and one purple state, Michigan, were also among this group.) All but one of these 13 states voted for Trump. Michigan swung from Obama to, narrowly, choosing Trump.

The states whose disease rates improved the least since 1990, heightening their risk relative to other states, were Alabama, Alaska, Arkansas, Indiana, Iowa, Kansas, Kentucky, Missouri and Oklahoma. The problem is grave: States with the worst heart-disease problems are only now achieving the CVD burden the healthiest states had in 1990. Mississippi continues to lag as the state with the largest overall CVD burden in the United States, more than twice the heart disease risk than Minnesota, the best state for heart health.

This was the first cardiovascular disease study to produce consistent measures for CVD burden and risk factors across all 50 states. The states were ranked using a common global health measure of disease burden born by a particular region, referred to as disability-adjusted life years — getting heart disease in your 40s counts more than getting it in your 70s or 80s.

Most of the changes can be accounted for using fairly common explanations of heart disease, from aging populations in states that are backsliding to regional differences in smoking rates and diet, Roth’s University of Washington team concluded. But the research suggests policy factors, like the decision in some states not to expand Medicaid health insurance for low-income families under the Affordable Care Act, may play a role. The ACA subsidized Medicaid expansion while leaving the decision to broaden coverage up to each state. But Roth said further study is needed to draw a direct line between the Medicaid issue and heart disease.

The JAMA paper is consistent with other recent studies highlighting how health disparities often track America’s increasingly familiar red-and-blue state divide. A study from the University of Wisconsin’s Applied Population Lab in June showed that white Americans are dying more rapidly than their replacements are being born in 26 of the 50 states. And a paper last year by other University of Washington researchers showed big geographical disparities in the rate of change in drug- and alcohol-related death, suicide and homicide — showing a shift in burden toward white and rural counties and away from cities, especially on drug-related deaths, including from opioids.

“If you don’t have a job and have no money, you have nutritional issues,’’ said Joseph Florence, director of rural programs at the East Tennessee State University’s Quillen College of Medicine in Johnson City, in the Appalachian part of the state near North Carolina. “The whole aspect of exercise in these communities is slim to none.’’

Roth and his co-authors estimate that 80 percent of heart disease burden can be accounted for by traditional heart-disease markers. Many poorer states, especially in the South, have always had higher rates of obesity and smoking than states in the Northeast and on the West Coast.

Another big factor in some areas is inconsistent access to health care, which means little preventive care and counseling on risk factors for heart disease, said Salim Virani, director of the Cardiology Fellowship program at Houston’s Baylor College of Medicine. In Texas, which has high rates of heart disease but isn’t one of the states to see incidence rise since 2010, as many as 21 percent of the population lack health insurance according to some surveys, well above a national rate that fell as low as 10.9 percent after passage of the Affordable Care Act in 2010.

“The ‘why’ question can only partially be answered by what we currently know,” Roth said.

One reason for high percentages of people lacking health insurance is states’ refusal to expand Medicaid eligibility.

“If people lose health-care access, they wait before coming to see a doctor,’’ Virani said.

The study authors said relative disparities between states may be of particular concern for states, including Alabama and Oklahoma, given decisions not to expand their Medicaid systems under the ACA. And many of the red states that did expand Medicaid are still engaged in political battles over the ACA. In June a court overruled Kentucky’s plans to add a work requirement to its expanded Medicaid — it was the first state approved by the federal government to take advantage of a Trump administration decision to allow states to force low-income individuals to work as a qualification for Medicaid. Arkansas and Indiana were also approved by the government for the work requirement; Arizona, Kansas, Mississippi and Utah were among the states that had applications pending at the time of the court decision. All are among the heart disease laggards identified in the study. There are concerns that the decision could lead other states to decide not to expand Medicaid at all.

Experts said the data point to the need to do more preventive care for heart disease risk factors. Florence points to programs that get providers out of hospitals and into the community, including in mobile settings like vans that offer screening and monitoring, as examples of what can be done. Others point to the need for a redoubling of efforts on smoking, and Virani said research is needed on whether smoking e-cigarettes will lead to teens switching to conventional tobacco.

Experts also want further study to get results on heart disease rates down to the county level, which will let them target resources better. Doctors also need to know more about the rise in obesity and diabetes that seem to be causing the slowed progress on health disease and to study best practices in counties and states that have kept up the improvement, said Seth Martin, director of the Advanced Lipid Disorders program at Baltimore’s Johns Hopkins Medicine.

“The frustrating thing is, we know how to prevent cardiovascular disease,’’ Roth said. “But we don’t always do these things, especially early in life.”