Middle-aged white Americans are at the center of a disturbing trend. Their death rates are rising significantly faster than any other racial or ethnic group, according to an analysis published in the Proceedings of the National Academy of Science.

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The study shows the most significant increase in death rates occurred in the 45-54 age range between 1999 and 2013. The findings fly in the face of what the general public has believed for many years — that mortality rates among white Americans were decreasing.

Reversing years of progress, mortality is again rising among middle-aged white Americans.

That’s not the only unexpected result of the study, either.

“Surprisingly, the causes of death are not the typical causes of death we’ve been focused on, such as obesity and smoking,” said Lis Nielsen, chief of the Individual Behavioral Processes Branch of the National Institute on Aging. The NIA funded the study.

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“Instead, in this case, the paper finds that the leading causes of death for this age group in the white population are suicide, substance abuse, liver diseases and cirrhosis,” Nielsen told LifeZette.

The study also produced other alarming statistics about deaths among white, middle-aged Americans.

“In those people who had a high school degree or less, the deaths that were caused by drug and alcohol poisoning rose four times compared to what they were in previous times,” Nielsen said.

Suicides among the lesser-educated middle-aged Americans rose 81 percent. That group’s dismal mortality rates were enough to spike the statistics for all of the middle-aged groups combined.

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The study’s authors conclude that “concurrent declines in self-reported health, mental health, and ability to work, increased reports of pain, and deteriorating measures of liver function all point to increasing midlife distress.”

Though the analysis provides no direct link between death rates and the economy, it has sparked speculation that difficult financial times could have been a factor in the higher numbers.

“Those people who are impacted by the recession most adversely in terms of the ability to find work are often those at the lowest end of the education ladder,” Nielsen said.

The findings on that particular group of people are a new development for the American Foundation for Suicide Prevention, but the rising rate of suicide comes as no surprise to Dr. Christine Moutier, the chief medical officer for the organization.

“That has been something on our radar that we’ve been talking about and trying to launch prevention efforts to address,” Moutier told LifeZette. “It’s another important part of the story about what’s going on with suicide and how we can intervene as a country.”

She also said the study helps suicide-prevention advocates highlight a major problem associated with their cause — funding.

“The level of federal investment in suicide prevention and suicide-related research is orders of magnitude smaller in comparison to the loss of life that suicide causes,” she said.

If you are thinking about suicide or have questions about how to prevent it, the AFSP has resources available, including a 1-800-273-TALK hotline.