Brothers and sisters of people who live to the ripe old age of 100 or more are much more likely to reach very old age themselves. But a new study zeroing in on a genetic component of extreme old age does not rule out the importance of environmental factors, such as a healthy lifestyle.
Known as centenarians, people who live to be 100 or more are usually in good health until the very end of their lives. Scientists who study the elderly, including Thomas Perls of Harvard Medical School in Massachusetts, are interested in finding out how to help everyone to enjoy a healthy old age.
It's long been suspected, but never proved, that those who survive to extreme old age have unique longevity genes.
Now, a study published in Proceedings of the National Academy of Sciences by Dr. Perls and colleagues comes a step closer to demonstrating the existence of an old-age gene. "We've been conducting a centenarian study since the early 1990s, and for some time we've been coming across brothers and sisters of our centenarians also getting to very old age," he said.
The researchers led by Dr. Perls collected data from 444 families that had at least one centenarian. Over 2,000 brothers and sisters were identified in the longevity group and compared to a randomly selected group of 2,000 men and women born at least 100 years ago.
Dr. Perls said investigators found that the siblings of the centenarians had half the risk of dying before age 100 compared to everyone else. "What that translated into is that the brothers of the centenarians had about a 17 times greater chance themselves of getting to be 100, and the sisters had about an eight and a half times chance of getting to be a hundred. In other words, exceptional longevity, not just longevity, but exceptional longevity, runs very strongly in families," he said.
The study found that brothers of the centenarians were vulnerable to premature death only twice in their lifetimes. The periods occurred during their teenage years and young adulthood years conceivably marked by wartime or when the young men might have died as a result of incurable disease.
Winifred Rossi is with the National Institute on Aging, which helped to fund the study. Ms. Rossi said the research is the first to show that siblings of centenarians have a significant survival advantage throughout their entire lives.
She said that could be good news for people with relatives who have survived to an extremely old age. "If you can look at families and see this, then there is some indication that there might be some familial patterns of long lived people. Whether or not it's genetic or it's environment or it's a combination of the two, we don't know the answer to that yet," she said.
Dr. Perls thinks environmental factors are less important for centenarians, who, he said, tend to smoke less and are thinner than the general population. But he said that doesn't mean everyone can't lead a full, healthy life.
"The trick is that we have to have better - much better - health related behaviors - not smoke, get the weight down, have a healthy diet and exercise. If we made major dents in those four things, I think many more of us would be living to quite old age in very good health. That's what the average set of genes is capable of achieving for us. To go the extra 15, 20 years beyond that, you may need these genetic booster rockets that we're hunting down," Dr. Perls said.
Last year, Thomas Perls and colleagues discovered a region on chromosome four in the same group of centenarians involved in the current study that appears unique to extreme old age.
The researchers are now trying to find one or more genes that may delay the onset of disease.