NEW YORK (Reuters Health) - The gains in human life expectancy over the past century-and-a-half have been nothing short of "astonishing," according to researchers. And, they say, there's no limit in sight.

This idea of ever-increasing longevity stands in contrast to the historical view that the human life span must soon hit a "ceiling," according to Jim Oeppen, of Cambridge University in the UK, and James W. Vaupel, of the Max Planck Institute for Demographic Research in Rostock, Germany.

However, through the years, forecasted limits to life expectancy have been proven wrong time and again, the researchers write in the May 10th issue of Science.

Currently, Japanese women hold the world "record" for average life expectancy, at nearly 85 years of age. In 1840, Swedish women topped the world, expecting to live to the ripe old age of 45.

Oeppen and Vaupel call this 40-year gain, which occurred steadily over time, perhaps "the most remarkable regularity of mass endeavor ever observed."

For 160 years, the researchers note, the top life expectancy has risen by a quarter of a year, each year. What's more, they claim, there is no reason to believe a leveling-off is imminent.

"If life expectancy were close to a maximum, then the increase in the record expectation of life should be slowing. It is not," Oeppen and Vaupel write.

And, they add, past predictions of the average human-life limit have proved wrong--such as a 1928 projection based on US data that, absent any "radical innovations," the ultimate life expectancy for men and women would be just shy of age 65.

But while this new outlook on life expectancy may sound good, Oeppen and Vaupel also point to some practical concerns. Currently, they write, private and public decisions--from choosing how much to sock away for retirement to setting policies on Social Security and other government programs--are based on the idea that life expectancy will soon hit a ceiling.

Instead, the researchers assert, it would be "reasonable" to assume the top life expectancy will keep growing by 2.5 years per decade, as it has in the past--in which case, the world's top average life expectancy will be age 100 in about 60 years.

They add, however, that such modest, steady increases "will never lead to immortality."

SOURCE: Science 2002;296.

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