Smoking is one factor driving the trend toward a lower life expectancy for women in parts of the U.S.

While life expectancy in the United States has risen steadily since the 1960s, a new study [published Tuesday] finds that in certain geographic areas of the country, life expectancy has stagnated, and even declined, especially among women.

From 1960 to 2000, life expectancy in the United States rose by seven years for men and six years for women. However, beginning in the 1980s, large geographic disparities began to appear.

The study analyzed health data from every county in the United States. According to lead author Majid Ezzati, Associate Professor of International health at Harvard School of Public Health  the "worst off" were among lower income Americans concentrated in the southern states.

He says in these communities race did not seem to affect life expectancy. "It is something associated with the way policies are implemented, with the way health systems are providing health services to people in different parts of the country or not providing services to people."

Ezzati points to chronic disease related to increases in smoking, high blood pressure and obesity as factors driving the trend. He says while much is known about how to manage these conditions, care is not reaching the people who need it the most. Women have experienced the most serious declines.

Over the last 20 years, life expectancy has either declined or stagnated for one of out every five women compared with four percent of men. Ezzati finds this a grim statistic for an industrialized nation. "We don't associate worsening of health, worsening of life expectancy with something that happens in a developed high-income country."

Ezzati says he saw such disparities after the fall of the Soviet Union and after the social networks fell apart in Eastern Europe. "That is the sort of thing that we see over long periods and what is happening with HIV/AIDS in some countries in Africa."

Ezzati says he hopes the study raises awareness about health care in America and pushes health officials and the public to monitor those being left behind. "That monitoring should be telling us something about what sort of interventions, what sort of policies can reverse this and then hopefully provide the resources for it."

Researchers from Harvard School of Public Health and the University of Washington  contributed to the study published in PloS Medicine.