For the first time since the Spanish influenza of 1918, life expectancy is falling for a significant number of American women and the cause seems to be obesity and smoking according to a new study.

The disturbing trend dis driven by increases in death from diabetes, lung cancer , emphysema and kidney failure and reflects the long-term consequences of smoking and points to the growing obesity epidemic.

12 Percent of U.S. Women Are Affected

In nearly 1,000 counties that together are home to about 12 percent of the nation's women, life expectancy is now shorter than it was in the early 1980s, according to the study.

Life Expectancy Explained

The Trends

The trend appears to be driven by increases in death from obesity related diseases such as diabetes, lung cancer, emphysema and kidney failure, along with the long-term consequences of smoking, a habit that women took up in large numbers decades after men did.

Because both trends are still increasing with women women's life expectancy could continue to decline broadly across the United States in coming years.

"I think this is a harbinger. This is not going to be isolated to this set of counties, is my guess," said Christopher J.L. Murray, a physician and epidemiologist at the University of Washington who led the study published in PLoS Medicine, the journal of the Public Library of Science.

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

The phenomenon appears to be not only new but distinctly American.

"If you look in Western Europe, Australia, Japan, New Zealand, we don't see this," Murray said. 

The Obesity Effect

Obesity has risen markedly in the past two decades, with women more affected than men. About 33 percent of women are now obese, compared with 31 percent of men. Extreme obesity is twice as common in women (7 percent) as in men (3 percent).

Being overweight greatly increases the risk of developing Type 2, or "adult-onset," diabetes and many other life shortening disease and conditions.

In recent years, the prevalence of high blood pressure has been increasing in women, as well -- partly the result of weight gain. In 1990, 42 percent of women older than 60 had hypertension; by 2000 it was 51 percent. (In men, the trend is still dropping, as it has been for several decades.)

"This is a story about smoking, blood pressure and obesity," said Majid Ezzati, of the Harvard Initiative for Global Health, a co-author of the paper.