Human Life Expectancy Nearing Limits

Reviewed by Charlotte E. Grayson Mathis, MD
From the WebMD Archives

Feb. 18, 2001 (San Francisco) -- When it comes to human aging, wild claims abound: New medical advances will cure the scourges of the centuries; vitamins, hormones, and antioxidants will preserve our tissues forever, and we'll all live to the healthy old age of 150.

Not exactly, according to a new study.

Though life expectancy rose dramatically during the 20th century, increasing 30 years in the last century, additional increases are likely to be incremental, says Jay Olshansky, PhD, a professor at the School of Public Health at the University of Illinois, Chicago, and senior research associate at the Center on Aging at the University of Chicago.

"Everyone alive will be long dead before a life expectancy of 100 years will be achieved -- if ever," he says.

Instead, Olshansky predicts that if current trends in death rates continue, the average life expectancy will reach 85 years in 2033 in France, 2035 in Japan, and in the year 2182 in the U.S. The life expectancy at birth for females in the U.S. was 79 years in 1995, the most recent data available, and the life expectancy for males was a few years lower.

The study will be published in Friday's issue of the journal Science. The limits of human aging were debated by a panel of experts here today at the 2001 annual meeting of the Annual Association for the Advancement of Science.

Biological limits of the human body will prevent further dramatic extensions of lifespan, says Leonard Hayflick, PhD, who more than 40 years ago uncovered a famous limit on the lifespan of noncancerous human cells called the "Hayflick limit." Hayflick is a professor of anatomy at the University of California, San Francisco.

Most of the discussion about aging that occurs today -- among both scientists and laypeople -- focuses on eradication of age-related diseases that kill elderly people, particularly cancer, heart disease, and stroke. But even healthy human tissue is designed to age and die -- a phenomenon little studied by scientists, Hayflick says.

"Even if we eliminate all [current] causes of death in elderly people, the increase in life expectancy will be no more than 15 years," he says.

And if that happens, people will again die of "old age," rather than a particular disease. In other words, at a certain point, their organs will simply give out, he says. "We'll need a new vocabulary of aging," Hayflick tells WebMD.

But other experts are more optimistic about extending the human lifespan, saying that a longer life expectancy is possible.

"You can't say that this can't happen, says Ronald Lee, MS, PhD, a professor of demography and economics at the University of California, Berkeley.

Lee advised the U.S. Social Security Administration last year that its projections for life expectancy were too pessimistic. The agency had estimated that by the year 2070, the average life expectancy in the U.S. will be 84 years.

But Lee says because the agency has had a record of underestimating gains in life expectancy, "a simple extrapolation of past trends may be the best way to go."

Those calculations predict that in 2070, average life expectancy for at birth will be 87.7 years.

If life expectancy increases more than the agency has estimated, it could dramatically increase the shortfall of funds to pay benefits for older Americans, Lee says.

Olshansky's study says that this is too optimistic, and that the original agency estimates are probably accurate.