July 1, 2010 -- Do you have what it takes to live 100 years -- or more?
A new test tells whether a person has the "genetic signature" of exceptional longevity. About 77% of centenarians -- people 100 years old or older -- have this genetic profile.
"Our genetic profile ... is essentially a picture, and one can interpret this picture in terms of how many exceptional longevity variants a person carries in his genetic code," study researcher Paola Sebastiani, PhD, of Boston University, says at a news teleconference.
A preliminary study suggests that about 15% of people of European descent have better than a 50% chance of seeing 100 candles on their birthday cakes.
But genes are not destiny. In industrialized nations, only one in 6,000 people -- 0.016% -- lives to age 100. And only one in 7 million people lives to be a "super centenarian" of age 110 or older. Clearly lifestyle choices, the environment, and plain luck have a lot to do with longevity, says Thomas T. Perls, MD, MPH, head of the New England Centenarian Study at Boston University.
"If 15% of people have an increased probability of living to 100, and they are not hit by a bus or killed in a war, maybe they get to fulfill that," Perls said at the news conference. "Now maybe these people need not to smoke and not to be obese and to have other lifestyle factors as well. So a lot goes into the question of whether 15% of the population will go on to be 100 or not."
Another factor that matters is sex: 85% of centenarians are women, Perls said.
Longevity Genes Trump Disease Genes
Nevertheless, having the exceptional longevity genetic signature is good news for anyone. The centenarians in the study remained healthy until the very end of their very long lives.
"We often think, 'Who would want to live to 100?'" Perls said. "But these people do not have Alzheimer's. In fact, 90% are disability free at an average age of 93. They compress their diseases to the very end of their lives. And super centenarians compress disease to even later in life."
That does not appear to be luck. Centenarians are just as likely as anyone else to have genetic risks for diseases of aging such as dementia, high blood pressure, diabetes, and stroke. But their exceptional-longevity genes seem to cancel out disease risks.
"The enrichment and presence of these longevity-associated genetic variants could trump or cancel the effect of some of these disease-associated variants," Perls said.
Sebastiani, Perls, and colleagues began their study by analyzing the genomes of 801 centenarians -- the world's largest collection of extremely old people. Eventually they identified 150 tiny genetic changes linked to extreme old age.
These changes did not point to any single longevity gene. Instead, the changes were scattered across the 23 chromosomes that carry the human genome. Genes carrying these genetic changes have a wide range of functions.
Sebastiani said that the researchers' next job will be to try to figure out exactly which body functions are enhanced or suppressed by exceptional longevity gene variants.
That may take some time. Few if any of the centenarians had all 150 of the genetic changes linked to longevity. Instead, they fell into about 19 clusters. One cluster had almost none of the 150 genetic changes.
That may explain why 23% of centenarians are not identified by the exceptional longevity profile. Sebastiani suggested that the study has not yet found all of the genetic variations that predispose a person to a very long life.
Longevity Gene Test?
The researchers will soon post a free tool on their web site that will allow anyone who knows their genome to see how many of the exceptional longevity gene variants they carry. But it's not at all clear what a person would do with this information.
"Is a test for exceptional longevity ready for prime time? I think a lot more study needs to be done as to what guidance doctors and others can give," Perls said. "What do you do when you're told you absolutely don’t have the signature for exceptional longevity? Do you go and do a lot of risk-taking behaviors and say, 'Well, I’m hanging it up'? Or does it give you an impetus to take all the more care of yourself and to recognize that you may well fall into the 23% of individuals who don’t have the signature but very well could go on to be 100?"
Sebastiani, Perls, and colleagues report the findings in the July 1 issue of the online journal Science Express.