From 1959 to 2016, U.S. life expectancy increased from 69.9 years to 78.9 years, but then began to decline after 2014. (Photo: Shutterstock)

U.S. life expectancy is decreasing due in large part to midlife deaths from drug overdoses, suicides and diseases brought on by smoking, obesity and stress, according to a study published in the Journal of the American Medical Association.

"Despite excessive spending on health care, vastly exceeding that of other countries, the United States has a long-standing health disadvantage relative to other high-income countries that extends beyond life expectancy to include higher rates of disease and cause-specific mortality rates," writes the lead author, Steven H. Woolf, director emeritus of the Center on Society and Health at Virginia Commonwealth University.

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From 1959 to 2016, U.S. life expectancy increased from 69.9 years to 78.9 years, but then began to decline after 2014, according to the study. While cause-specific mortality rates among adults aged 25 to 64 years had started to rise in the 1990s, the midlife mortality rate for all causes began to increase in 2010. By 2014, that began to impede on the U.S. life expectancy rate.

From 2010 to 2017, midlife all-cause mortality rates rose from 328.5 deaths/100,000 to 348.2 deaths/100,000. By 2014, midlife mortality was increasing across all racial groups, caused by drug overdoses, alcohol abuse, suicides and a diverse list of organ system diseases.

Some regions of the country are much more affected by others, the researchers found. The largest relative increases in midlife mortality rates occurred in New England (New Hampshire, 23.3 percent; Maine, 20.7 percent; Vermont, 19.9 percent) and the Ohio Valley (West Virginia, 23.0 percent; Ohio, 21.6 percent; Indiana, 14.8 percent; Kentucky, 14.7 percent).

The increase in midlife mortality during 2010 to 2017 was associated with an estimated 33,307 "excess U.S. deaths," 32.8 percent of which occurred in four Ohio Valley states. Excess deaths means the actual number of deaths for a certain age group above the expected mortality rate for that group.

Woolf cautions that more must be studied to determine why the U.S. is falling behind other countries.

"Moving from speculation to evidence about root causes will require innovative research methods, including cohort studies, multivariate modeling, investigation of migration effects, and the application of machine learning to historical data sets," he writes. "Fully understanding the timing of U.S. mortality trends will also require interdisciplinary research involving epidemiology, demography, sociology, political science, history, economics, and the law. Clarifying the role of state policies may be especially important, given the divergent state trajectories reported here."

Read more: 

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• Top 5, bottom 5 countries for life expectancy and where the U.S. ranks
• Suicide may be key factor in growing death rate