Ezzati M, Friedman AB, Kulkarni SC, Murray CJL (2008) The Reversal of Fortunes: Trends in County Mortality and Cross-County Disparities in the United States. PLoS Med 5(4): e66.doi:10. 1371/journal.pmed.0050066. 
This study using mortality statistics from the NCHS (National Center for Health Statistics) documents an increase in mortality inequality across US counties between 1983 - 1999, indicating an increase in mortality in counties of the deep south along the Mississippi River and Appalachia.  When comparing the 2.5% of counties with the lowest life expectancies and the 2.5% of counties with the highest life expectancies, the difference in life expectancy was 11 years for men and 7.5 years for women in 1999.  After 1983, gain in life expectancy was positively associated with county income.  Gender differences found were that HIV/AIDS and homicide deaths in young and middle-aged men was a major contributor to male but not to female, life expectancy decline.  For women, the decline in female life expectancy was caused by increased mortality from lung cancer, COPD, diabetes and other chronic diseases related to smoking, obesity and high blood pressure.  When race-specific cross-county analysis was considered, the geographical mortality disparities were applicable for both white and black populations.  The impact of migration on mortality disparities was discussed.  This research suggests that reversal of the risk factors for chronic disease and injury in these worst off counties and regions should be investigated and monitored.   
 

See the summary article at Kaisernet.org: Life expectancy declines in some U.S. populations, primarily those in deep south, Appalachia, study finds.