U.S. researchers say a specific set of genes may be the reason some people live to 100 years or more. They have published a study of more than 300 very old people indicating that these elderly possess such longevity genes. The genes are still undiscovered, but the researchers have traced their location to a specific region on the genetic material known as chromosomes.
Living to a ripe old age appears to be more than just a matter of taking good care of yourself. It seems that you need to be lucky enough to have a genetic predisposition for extreme longevity, too.
Physician Thomas Perls of Boston's Beth Israel Deaconess Hospital says genes probably account for longevity because it runs in families.
"Centenarians are very rare. They are about one per 10,000 in the population," said Dr. Perls. "So when you find a bunch of them within a single family, then it really takes on a genetic flavor,"
To find out for sure, Dr. Perls and a team of researchers from several Boston and New Jersey institutions studied 137 sets of very old brothers and sisters, most of European descent. The oldest sibling in each set ranged from 98 to 109 years old. The youngest in each was at least 91.
What the scientists were looking for in all the brother and sister groups were regions in their genetic material, called chromosomes, that were chemically identical. The presence of identical regions would be a strong hint that they are linked to longevity, containing a gene or genes promoting old age.
Dr. Perls and his colleagues report in the Proceedings of the National Academy of Sciencies that they found such a region shared by most of the sibling groups on chromosome four.
"Within that region, we suspect that there is a gene that is important for the ability to get to exceptional old age - probably one of at least 10 genes that seem to be important," said the researcher.
The number is far fewer that the 1,000 genes that scientists have thought could influence the human lifespan. Why so few?
Dr. Perls explains that "aging is an extremely complex syndrome of interaction among thousands of genes and our environment. It's quite complex. But to live the additional 20 to 25 years beyond what, on average, we're all capable of achieving, we think, requires a distinct survival advantage, and that may translate into a relatively few number of genes that help people age more slowly than the rest of us," he said.
The genes in question remain undiscovered. The researchers say studies of dozens more centenarian families are needed to find the subtle genetic variations that allow them to live so long.
The executive director of Institute for the Study of Aging, Dr. Howard Fillit, believes whatever genes are involved have something to do with suppressing disease.
"What appears to be happening is these people are somehow protected against the bad things that cause people to die at younger ages," suggests Dr. Fillit. "So at the genetic level, this gene is thought of as a positive gene that helps people avoid the diseases of old age."
Genes produce proteins that carry out their instructions in the body. Dr. Fillit says discovery of a longevity gene or genes could possibly lead to drugs that could mimic the effect of the proteins in people without the genes.
Yet he refrains from equating such a drug with a fountain of youth, noting that "these people that are over 100, they are not youthful in any way. They are frail. They are not running marathons."
However, Dr. Perls says his group is not seeking a fountain of youth, but the fountain of aging well. "If one can do what these centenarians are doing, it would be a boon for us all," he said. "It would be tremendous."