Life expectancy falls in many parts of U.S.: Why?

(CBS/AP) Americans are living longer than ever before, with life expectancy in the U.S. at an all-time high. But we can't all rejoice. A new study shows that in hundreds of U.S. counties - mostly in the South - life expectancy has fallen.

A baby born in 2009 could expect to live 78 years and 2 months, the CDC recently estimated. But the CDC doesn't calculate estimates by county. And Dr. Christopher Murray, a University of Washington researcher and editor of the online journal "Population Health Metrics," says, There are enormous variations within the country."

A recently published study in the journal found that life expectancy for women fell significantly in 702 of the nation's more than 3,100 counties. For men, life expectancy dropped in 251 counties. In 158 counties, life expectancy dropped for both men and women.

The largest declines - by nearly two years - were in Mississippi's Madison County, near Jackson, and eastern Oklahoma's Hughes and Okfuskee Counties, for women. Kentucky's Perry County in Appalachia and Mississippi's Madison had the biggest drops for men.

Why are life expectancy estimates rising in some counties and falling in others? Murray and his colleagues say it's not issues like poverty or racial makeup that explain the difference, but high rates of obesity, smoking and other preventable health problems.

Some experts disagree, saying the findings may be tied to the availability of good health care or with the migration of healthy people from one place to another. But Murray said his research finds migration theories are not the answer - there's been little movement in or out of most places with the lowest life expectancy. In several cases, counties with plummeting life expectancy were next to or very near counties with rising longevity.

Where should you live if you want the best shot at a long life? Metro areas with lush jobs and universities - Georgia's Fulton County (Atlanta), Washington, Alexandria, Va., and New York City for men - or Alexandria and a Wyoming county home to the affluent Jackson Hole, for women.