The mortality rate for middle-age white Americans is going up — contrary to what's happening with everyone else in the world — and a provocative new report explores why.

Between 1999 and 2014, deaths among white Americans between 22 and 56 increased at the same time that life expectancy figures across the globe were going up, according to a study in the Proceedings of the National Academy of Sciences.

Heart disease, diabetes and respiratory disease are among the conditions that have contributed to rising death rates.

"Upon further digging, we find a multifaceted phenomenon, where mortality rates for middle-aged whites have stopped declining — or actually increased — across a broad range of health conditions, including most of the leading causes of death for this group," researchers wrote in the Commonwealth Fund report.

Hardest hit were those living in seven Southern states. Whites lacking a four-year college degree also were especially vulnerable, the authors wrote in their report, "Mortality trends among working-age whites: The untold story."

"The notion that changing social and economic forces are a possible explanation does not mean that white middle-aged adults are suddenly worse off than other groups," the report said. "Rather, it suggests that their lives have changed in unexpected ways in recent years."

The study cited the following underlying causes: "less-educated workers' increasing disengagement from the mainstream economy; declining levels of social connectedness; weakened communal institutions, and the splintering of society along class, geographic and cultural lines."

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Allie Shah • 612-673-4488