For the first time since the Spanish influenza of 1918, life expectancy is falling for a significant number of American women.

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 a study published today.

"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. It is being published in PLoS Medicine, an open-access journal of the Public Library of Science.

The study found a smaller decline, in far fewer places, in the life expectancy of men in this country. In all, longevity is declining for about 4 percent of males.

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.