If age and gender-specific trends in death rates observed from 1985 to 1995 continue, the authors say, life expectancy at birth for males and females combined would not reach 100 years until the 22nd century in France and Japan, and the 26th century in the United States.

Our personal hopes and fears about human longevity aside, projections of human-life expectancy are critically important to public policy. In the United States, the Social Security Administration and Census Bureau make these projections that have a profound impact on the future solvency of national trust funds including Social Security and Medicare.

Using the latest data on death rates and life expectancy for men and women of all ages in Japan, France and the United States from 1985 to 1995, the authors found that while many people are living longer, the rise in life expectancy is slowing down.

"This is not surprising, because life expectancy is very difficult to increase once it approaches 80 years," Olshansky says. Why? "Because adding decades to the lives of people who have already lived for 70 years or more is far more difficult then adding decades to the lives of children who are dying of infectious diseases," he explains.

The authors are optimistic that people will continue to live longer and they expect to see a dramatic increase in the retirement-age population with the aging of the baby-boom generation. The next quantum leap in life expectancy, however, can occur only if "biomedical researchers can discover how to modify the aging process and make such a discovery widely available to the entire population," the authors say in the Science article.

To forecast life expectancy, Olshansky and his coauthors, Bruce Carnes of the National Opinion Research Center at the University of Chicago and Aline Désesquelles at the Institut National d'études Démographiques in Paris, employed a biodemographic approach -- one that takes into consideration biological as well as statistical factors.

"The purely mathematical approach often used to make such forecasts may not violate any mathematical rules," Carnes says, "but when used to forecast life expectancy over a long time period, this approach ignores the biological forces and biomechanical constraints that influence how long people are capable of living."

In research published in Science in 1990, the authors demonstrated empirically that as life expectancy at birth rises, it becomes less sensitive to changes in death rates. They concluded then that the practical upper limit to life expectancy is 85 years (88 for women and 82 for men).

Since then, other scientists have declared that these estimates are too pessimistic and suggested, instead, that death rates would begin declining dramatically and that life expectancies approaching 100 years were plausible in the 21st century.

"A decade has passed since we made our forecasts," Olshansky says, "so there is sufficient evidence now to determine whether the rise in life expectancy has accelerated as others had predicted, or decelerated as we had predicted."

The authors estimate that life expectancy at birth for males and females combined would reach 85 years in 2033 in France, 2035 in Japan and 2182 in the United States.

The authors point out that the popular view that the United States fares better than the rest of the developed world when it comes to old-age mortality may no longer be true.

Recent evidence suggests that death rates for people age 80 and older are increasing much more slowly in the United States than in other countries such as Japan and France, the authors say. They add that death rates among U.S. males age 89 and older increased between 1985 and 1995.

The authors conclude, as they did a decade ago, "future gains in life expectancy will eventually be measured in days or months rather than years."

They recommend that the time has come to focus our attention more on quality of life rather than on length of life, and that a more reliable measure of a population's health is already available. It is a measure referred to among scientists as "health expectancy." - By Jody Oesterreicher

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University of Illinois at Chicago

[Contact: Jody Oesterreicher]

20-Feb-2001