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How will we age?


(CNN) -- Catherine McCaig is 103 years old. Widowed 65 years ago, she lives a busy life, alone in Marshfield, Massachusetts. Her 95-year-old sister Winifred Whynot lives two doors away and comes over to visit nearly every day for a home-cooked meal.

The two sisters are being studied by Dr. Thomas Perls, a gerontologist at Harvard Medical School. He suspects there are genes in their family that have allowed them to reach such an advanced age in remarkably good health. Their brother Nat lived to 93.

Indeed, genetic research has made some amazing strides in recent decades -- pinpointing genes that make some people more susceptible to diseases like cancer. But beyond genes for specific diseases, scientists are narrowing in on a set of genes that seem to allow a rare group of people to age more slowly. Their theory is that a sort of natural clock ticks down as we grow older. And understanding how it works could help us slow that clock down for future generations.

In the next millennium, most people will be averaging life spans of 150 years.

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Dr. Perls says his team has recently discovered about ten families who are "highly clustered" for longevity. Such families, he says, often have five or six siblings that have lived upto the age of 100 years or more. "You can narrow it down to very few genes being responsible for that trait," he says.

Dr. Perls -- whose own great-grandmother lived to 102 -- believes centenarians may unlock the secret to old age. "We've quickly found out how incredibly healthy centenarians have to be the vast majority of their lives to get to their age.... (they) in fact escape various diseases associated with aging and they have a history of aging very slowly."

Dr. Perls, who co-authored the book "Living to 100", is investigating how people can delay the late-life decline in health until extreme old age.

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  • Early research ruled out lifestyle as the single reason for long lifespans because centenarians have little in common -- except that most have never smoked. For instance, Whynot says neither she or her sister drink or smoke. "We are very lovely people," she says with a laugh.

    A few years ago, Dr. Perls began to hunt for a set of genes that would account for extreme longevity. Dr. Perls and his colleagues have been collecting blood samples and mapping the genes of centenarians around the country.

    "We have one woman who's the oldest person in the world actually, Sarah Knauss who's in our study at age 118. She has a great-great-great grandchild." To pinpoint longevity genes in humans, scientists are turning to nematodes -- or tiny worms. Dr. Gary Ruvkun, a geneticist at Massachusetts General Hospital, says that researchers can mutate genes in the worms that will lead to a longer lifespan.

    Nematodes carry in their genes a kind of program that determines their lifespan. By using chemicals and radiation to mutate those genes, Ruvkun has created worms that live as much as five times longer -- 100 days instead of the normal 20.


    "Fifty percent of the worm genes look like our genes," says Ruvkun. "It means that the mechanisms that govern many things in life were invented before we diverged from worms, were invented more than six hundred million years ago...That means that if you study how a lifespan operates in a worm you're actually studying much of how lifespan operates in us. "

    Ruvkun says ultimately his findings may point to hormones that serve as a kind of time clock regulating how long we live and could lead to an injection that wards off aging, just as insulin fights diabetes. "We believe that the genes that we are identifying are pointing to human genes that will also be able to lengthen human lifespan. Whether they will be able to lengthen that lifespan to the same degree, three or five-fold, we just really don't know."

    National Institute on Aging
    State and local agencies on aging
    Alzheimer's Disease Education and Referral Center

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