Multiple studies have revealed that the life expectancy of women in the United States has declined in recent decades, leaving experts searching for the cause.

Research published in March by University of Wisconsin researchers David Kindig and Erika Cheng found that female mortality rates went up in nearly half of U.S. counties between 1992 and 2006. For men, only 3% of counties witnessed increases in male mortality over the same period.

“I was shocked, actually,” Kindig told The Atlantic. “So we went back and did the numbers again, and it came back the same. It’s overwhelming.”

A few months later, a report by University of Washington researcher Chris Murray and four co-authors found that female life expectancy had either remained the same or declined in 45% of counties from 1985 to 2010.

“Taken together, the two studies underscore a disturbing trend: While advancements in medicine and technology have prolonged U.S. life expectancy and decreased premature deaths overall, women in parts of the country have been left behind, and in some cases, they are dying younger than they were a generation before,” Grace Wyler wrote for The Atlantic.

“The worst part is no one knows why,” she added.

The Kindig study indicated a correlation between mortality rates and geography, with rising female death rates occurring throughout parts of the South and in the Great Plains, while the Northeast and the Southwest did not experience this problem.

A third study, published last year, showed a link between education and health in concluding that life expectancy for white female high-school dropouts had gone down significantly over the past 18 years.

Wyler wrote that these women “are now expected to die five years earlier than the generation before them—a radical decline that is virtually unheard of in the world of modern medicine.”

Jay Olshansky, lead author of the 2012 study, agreed, telling Wyler: “It’s unprecedented in American history to see a drop in life expectancy of such magnitude over such a short time period.”

“I don't know why it happened so rapidly among this subgroup. Something is different for the lives of poor people today that is worse than it was before,” Olshansky said.

-Noel Brinkerhoff

To Learn More:

U.S. Women Are Dying Younger Than Their Mothers, and No One Knows Why (by Grace Wyler, The Atlantic)

Even As Mortality Fell In Most US Counties, Female Mortality Nonetheless Rose In 42.8 Percent Of Counties From 1992 To 2006 (by David A. Kindig and Erika R. Cheng, Health Affairs) (abstract)

Left Behind: Widening Disparities for Males and Females in US County Life Expectancy, 1985–2010 (by Haidong Wang, Austin E Schumacher, Carly E Levitz, Ali H Mokdad and Christopher JL Murray; Population Health Metrics)

Differences In Life Expectancy Due To Race And Educational Differences Are Widening, And Many May Not Catch Up (by S. Jay Olshansky, Toni Antonucci, Lisa Berkman, Robert H. Binstock, Axel Boersch-Supan, John T. Cacioppo, Bruce A. Carnes, Laura L. Carstensen, Linda P. Fried, Dana P. Goldman, James Jackson, Martin Kohli, John Rother, Yuhui Zheng and John Rowe; Health Affairs) (abstract)

White Women in U.S. Live 10 Years Longer than Black Men (by David Wallechinsky, AllGov)

U.S. Life Expectancy Hits Record High (by David Wallechinsky and Noel Brinkerhoff, AllGov)