We're growing older...but don't smoke that success cigar yet and count on reaching 100 

KANSAS CITY, Mo. -- A glance at the latest charts on life expectancy seems to affirm a popular idea that Americans are speeding toward life beyond age 100.

In the "Chartbook on Trends in the Health of Americans 2006," published by the National Center for Health Statistics, are upward trajectories dating to 1900: Life expectancy at birth climbed in that time from 48 to 75 years for men and from 51 to 80 years for women.

But for all you baby boomers just hitting 60, don't assume your last will and testament can wait. Demographers who know the pitfalls of predicting longevity are tangled in a debate that casts doubt on the likelihood of old people growing much older than ever before.

The distortion in life expectancy numbers, said researcher John Bongaarts, vice president of the New York-based Population Council, "is largely due to steep reductions in infant and childhood mortality" over the decades.

Since 1950, death rates among infants have plunged 76%. Typhoid and other once-common killers of the young -- diseases linked to poor sanitation -- no longer weigh down the life-expectancy averages.

Remove those factors, and researchers find that U.S. life expectancy continues to climb but by no more than a couple of months annually.

"We are going to live longer," Bongaarts says, "but at a very slow pace."

Climb may be short-lived

The spiraling of life expectancy through the ages has spurred an industry of hopeful books such as "Healthy at 100," seminars such as "The 120 Club: Living the Good Life for 120 Years," and Web sites with "lifespan calculators" to magically ascertain the length of your own life.

Still, many experts believe we're approaching a biological ceiling for old age, and some even expect the longevity curves to start heading down.

Consider that in 1850, a white American man lucky enough to reach 60 could be expected to live 16 more years on average to age 76, federal health estimates show. In 2004 the law of averages suggested he could bank on living a few weeks short of 81.

Despite trillions of dollars spent on making Americans healthier, white male seniors have gained only five years since the era of cholera epidemics. White women chalked up seven extra years.

"Even if you add five or six years of life expectancy for people who reach their 60s, that's not trivial," says S. Jay Olshansky, an epidemiology professor at the University of Illinois' School of Public Health in Chicago. "But, certainly, to extrapolate overall life expectancy and say that we or our kids are going to live to 100? That's ridiculous."

By many calculations, life expectancy at retirement age has climbed about five years since Social Security arrived in the 1930s.

Olshansky is among a group of public-health prognosticators who foresee U.S. life expectancy reversing course "in a couple of decades," as higher rates of obesity take their toll.

That prediction, too, has statisticians arguing and policymakers perplexed about the effects of old-age projections on, say, Social Security and Medicare disbursements. The management of both programs -- and life insurance plans and corporate pensions -- hinges on educated guesses of when we will die.

First, forget about life expectancy being exact.

The standard formula has existed for centuries: Record the ages of death for a sample population over a period of time, average out the death rates by age and arrive at what demographers call "period life expectancy at birth."

For Americans born in 2003, the figure was 74.6 for male babies and 79.9 for female babies, the Centers for Disease Control reports.

Yet experts say those statistics don't make real sense: They factor in the deaths of 2003 and assume a medical and societal deep-freeze through the lifespan of babies born that year.

"You're saying nothing changes from here on," Ron Gebhardtsbauer of the American Academy of Actuaries said.

Things could change

Better hygiene in the early 20th Century helped conquer childhood afflictions. Then, in a single year, the influenza outbreak at the tail end of World War I sent life expectancy plummeting to below 40.

It wasn't until the last half of the century that medical advances and less smoking began to help significant numbers of elderly Americans live longer, only to suffer and die from Alzheimer's disease. But could stem-cell research fix that?

The World Health Organization recently issued a report that predicts AIDS will be the third-leading killer by 2030, behind heart disease and stroke.

"In all this talk of living to 100, there's been no discussion at all of the return in recent years of infectious diseases we thought were gone -- organisms that have grown resistant to antibiotics," said Olshansky, the epidemiologist.

FACTS ABOUT AGING