Americans’ life expectancy is stagnating or falling as obesity, high blood pressure, different cancers and other chronic conditions appear to claim more people’s health or life each year, a study published Monday revealed.

Researchers at Harvard School of Public Health and the University of Washington gathered data for every year between 1961 and 1999 (from the National Center for Health Statistics and the U.S. Census Bureau) and concluded that while Americans are living longer than ever on average, life expectancy is changing at increasingly unequal rates among the population.

The study found that 4 percent of the male population and 19 percent of the female population experienced either declines or stagnation in their life expectancy in the ‘80s and ‘90s. Although this deadly trend is mostly centered in the southern parts of the nation, several largely rural counties in Washington – Cowlitz, Lewis, Benton and Grays Harbor – are also on the verge of seeing a decline in overall life span.

“There has been increasing disparity in the U.S. population for two decades. The people who are worst off are either not getting better or are worse off,” Majid Ezzati of the school’s department of population and international health, who led the study, said as quoted by Reuters.

The study comes eight months after the U.S. Centers for Disease Control and Prevention reported that U.S. life expectancy has risen to almost 78 years in 2005 – up from 75.8 years in 1995 and 69.6 years in 1955. The U.S. ranks around 42nd in the world in life expectancy. The CDC report noted, at the time, that U.S. whites will live longer than blacks and women longer than men, conclusions that are clearly different from the new study.

“Female mortality increased in a large number of counties, primarily because of chronic diseases related to smoking, overweight and obesity, and high blood pressure,” the researchers wrote in the Public Library of Science journal PLoS Medicine.

“This was a complete surprise,” said Dr. Chris Murray, co-author of the study and director of the UW's new Institute for Health Metrics and Evaluation in the Department of Global Health. “It's remarkable in the history of the U.S.”

Starting with the ‘80s, people were at greater risk of dying as smoking, obesity and high blood pressure began exacting greater tolls. Specifically, women's deaths from lung cancer, diabetes and lung disease outpaced the drop in deaths from heart diseases, which had propped up overall female life expectancy during the 1960s and 70s.

For men, on the other hand, higher death rates from HIV/AIDS and homicides among young and middle-age males, as well as rising mortality from diabetes, cancers and lung disease, were largely offset by continuing gains against cardiovascular diseases.

“The data demonstrate a very alarming and deeply concerning increase in health disparities in the United States,” said Elizabeth G. Nabel, director of the National Heart, Lung and Blood Institute of the National Institutes of Health.

Most of these disparities are also a sign that “the health and social system have failed, as has been the case in parts of Africa and Eastern Europe,” Murray said. “The fact that is happening to a large number of Americans should be a sign that the U.S. health system needs serious rethinking,” he added.