Christopher Wanjek is the author of the books "Bad Medicine" and "Food At Work." His Bad Medicine column appears each Tuesday on LiveScience. [ Bad Medicine Column Archive

Researchers have found the unexpected in U.S. life expectancy: We might have peaked.

Life expectancy rates rose for most of Americans over the last four decades by about six years, from an average of about age 71 to age 77. Yet a sizeable portion of the population, mostly in rural regions, saw those modest gains level off and even reverse starting in the 1980s. This is in contrast to all other industrialized nations.

Nearly 20 percent of American women, in fact, experienced either stagnation or a decline in longevity, what researchers at Harvard School of Public Health and the University of Washington call a "reversal of fortunes."

A team led by Harvard's Majid Ezzati published these findings today in the online medical journal PLoS Medicine. The analysis — the first to look at mortality trends county by county — is based on mortality data from the National Center for Health Statistics and population data from the U.S. Census Bureau between 1959 and 2001.

Living large, and less

The findings are troublesome, the researchers said, because life expectancy, along with infant mortality, is a major indicator of the health of a nation. A decline in life expectancy, as is seen during turmoil such as war and famine, is a sign that health and social systems are failing.

This failing trend could easily spread to the rest of the nation, meaning that for the first time in the history of this country, parents will have lived longer than their children.

Hardest hit are regions in the Deep South, along the Mississippi River, in Appalachia and also the southern part of the Midwest reaching into Texas. The culprits — largely preventable with better diet and access to medical services — are diabetes, cancers and heart disease caused by smoking, high blood pressure and obesity.

Two Americas

The U.S. life expectancy already is nothing to brag about. The United States is the wealthiest country on earth, yet the life expectancy of its people is only about 78 years, which places us 41st on the 2008 CIA World Factbook list, behind Bosnia but still edging out Albania.

What the new analysis reveals is the reality of two Americas, one on par with most of Europe and parts of Asia, and another no different than a third world nation. For example, previous research has shown that the U.S. state of Georgia has a life expectancy and infant mortality rate similar to the impoverished Eastern European nation of Georgia. In Harlem, African American men are less likely to reach the age of 65 than men in Bangladesh, according to a study published in the New England Journal of Medicine.

The United States might still be the destination for complicated surgery and cutting-edge procedures, but for the most part it fails its poorest citizens, with about 36 million of them (12 percent of the population, according to the CIA World Factbook) living below the poverty line. As a result, the U.S. healthcare system ranks 37th on a list of 191 systems compiled by the World Health Organization.

Science can't increase life expectancy forever; good ol' inequality will trump it every time. The new longevity analysis should be a wake-up call for voters that this nation isn't No. 1. Maybe it doesn't need to be No. 1, but, given our vast resources, it would be nice to strive for something better than 41st place.

Christopher Wanjek is the author of the books “Bad Medicine” and “Food At Work.” Got a question about Bad Medicine? Email Wanjek. If it’s really bad, he just might answer it in a future column. Bad Medicine appears each Tuesday on LIveScience.