The health gains that continue to drive down death rates in most of the developed world have stalled for white Americans.

They’re dying younger—and in greater numbers—than historical trends would predict. The death rate for whites aged 45 to 54 declined by about 1.8 percent annually from 1983 to 1998, but it increased by 0.6 percent annually from 1999 to 2014. While an increase in drug overdoses and suicides accounts for part of the reversal, progress on reducing deaths from such causes as heart disease and cancer appears to be stagnating for white adults in the 21st century, according to an analysis from the Commonwealth Fund, a nonprofit that advocates for greater health-care access.

“We are witnessing a regression that has little precedent in the industrialized world over the past half-century,” the authors wrote.

The report builds on a startling paper from Princeton economists Anne Case and Angus Deaton that got a lot of attention late last year. They found that since 1999, death rates among middle-aged whites in the U.S. reversed a decades- long decline, driven by drug overdoses, suicides, and  diseases linked to alcohol. Case and Deaton, a Nobel Prize winner, reported the biggest jumps in mortality among the lowest- educated whites. The trend wasn’t evident in other rich countries or other racial groups in the U.S.

Since the end of World War II, most of the developed world has recorded steady improvements in mortality. Advances in public health, new medical treatments, and expanded access to health insurance help people live longer. Behavioral changes such as declining smoking rates also play a role. These add up to about a 2 percent annual drop in death rates.

“It’s been the historical norm for a long time,” said David Squires, co-author of the Commonwealth Fund report. 

Whites in the United States have historically had lower mortality rates than blacks. That continues to be the case by a large margin. But while mortality for black adults continues to decline across age groups, that’s not the case for whites. (Hispanics have lower death rates than both whites or blacks in the U.S., despite generally lower socioeconomic status, a demographic phenomenon known as the Hispanic paradox.)

The reasons behind white Americans’ mortality backslide aren’t clear. "We need to understand why this is happening,” said David Blumenthal, president of the Commonwealth Fund and co-author of the report. He and Squires hypothesize that the health declines mirror economic and social dislocation. Middle- aged whites in 2014 were more likely to be poor and less likely to be married than they were in 2002. Until 2014, when provisions of the Affordable Care Act took effect, they were more likely to be uninsured, too.

While the trend is national, it’s most pronounced in some Southern states, including Alabama, Arkansas, Kentucky, Mississippi, Oklahoma, Tennessee, and West Virginia. They’re the areas of the country with the weakest health systems, according to indicators compiled by the Commonwealth Fund.

Nan Astone, a researcher at the Urban Institute, observed last year that the death rates for white women from 15 to 54 had increased since 1999. While there isn't clear evidence, she posited that economic forces may play a role. “For working class people, wages have been stagnant for years now,” she said. “There’s been a lot of difficulty with globalization, frankly."