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By analyzing the heredity of the world's oldest people, Boston University scientists said Thursday they have discovered a genetic signature of longevity. They expect soon to offer a free test that could let people learn whether they have it in themselves to live to a very old age.
The new finding demonstrates that subtle variations in many genes may be responsible for some differences in life spans, offering complex patterns of protection against the ravages of normal aging.
"This is an extremely complex trait that involves many processes," said lead researcher Paola Sebastiani, a biostatistician at the university's School of Public Health. Even so, "we can compute your specific predisposition to exceptional longevity."
Rosa Rein, born on March 24, 1897, celebrates her 112th birthday at a home for the elderly in Lugano's Paradiso district in this March 24, 2008 photo.
The researchers, who studied more than 1,000 people over the age of 100, said they have no plans themselves to patent the technique or profit from it. Instead, they expect to make a test kit openly available as a research tool.
"This is a major breakthrough," said Nir Barzilai, director of the Institute for Aging Research at the Albert Einstein College of Medicine in New York, who studies the genetics of longevity but was not involved in the project. "It shows you that 150 markers [among millions] are all you need to distinguish between people who live to 100 and people who don't."
Scientists have long sought to crack the genetic code of healthy aging. On average, people in developed countries today can expect to live between 80 and 85 years, largely as a result of improvements in diet and pubic health. But the oldest of the old—"wellderly"—live decades longer, often free of the mental and physical ailments of age.
The oldest person alive today is 116 years old, according to the Los Angeles Gerontology Group. The oldest person on record lived to be 122 years old. But such people are one in a million.
No one knows the complete prescription for a healthy long life. But genes that help control cellular responses to famine, drought and other survival stresses may play a key role in staving off the diseases and chronic ailments of aging, research suggests.
While a healthy lifestyle is paramount, such genetic factors appear to become more important the longer we live. Indeed, a variation in even a single key gene called FOX03A can triple the chances a person may live past 100, researchers at the Pacific Health Research Institute in Hawaii recently reported.
In research published online Thursday by the journal Science, BU geriatrician Thomas Perlsand his colleagues studied variations in the biochemical code of DNA drawn from members of the New England Centenarian Study, considered the world's largest comprehensive study of these long-lived people and their families.
The scientists compared patterns of genetic variation in these elderly to those among people who lived more average life spans.
Among these healthy centenarians, the researchers identified a set of 150 unique genetic variations that, taken together, appear to highlight genes that protect against the ravages of age. This hereditary pattern is a measure of potential. Depending on personal habits, diet, injuries, accidents and other factors, these genes boost an individual's chances of survival in the lottery of life, the scientists reported.
The researchers acknowledged they didn't yet know all of the actual genes involved or how they affect human metabolism. The genetic markers are scattered across the entire three billion DNA characters of the human genome and touch on at least 70 known genes.
Nonetheless, the information allowed them to identify those predisposed to exceptional longevity with 77% accuracy in controlled tests, they reported.
"Now, we are going to have to find out what all these genes are, what they do and if there is a way we can affect them," said geriatrics expert Bradley Willcox, who was not involved in the Science paper. He is a principlal investigator of the Hawaii Lifespan study and the Okinawa Centenarian Study, which involve analysis of thousands of aging men.
In the meantime, the BU researchers said they plan to offer a free version of the longevity test later this month through a public website maintained by the New England Centenarian Study.
But the scientists warned that their experimental procedure might reveal more than some people would like to know. Genetic testing often reveals tantalizing but incomplete information about our risk for disease, and medical ethicists caution that it's difficult to know how to act on the information. Clues about our life span, for example, could affect decisions about insurance coverage or long-term medical treatments.
"I don't think people are ready for this from a social point of view," said BU's Dr. Perls, who was a senior author of the study. "But I don't think that will stop companies from trying to market this," he added.