In the hopes of uncovering the genetic basis for extremely long life spans, scientists have sequenced the genomes of 17 of the world's oldest living people.
Participants ranged in age from 110 to 116, and all but one were female. Many of these so-called "supercentenarians" were physically and cognitively fit into their old age — one participant practiced as a doctor until age 103, and another drove a car until age 107.
The ultimate goal of the research is to figure out how supercentenarians are able to "slow down the aging clock," said study co-author Stuart Kim, a professor of developmental biology at Stanford University. If researchers are able to figure that out, they might be able to create a drug or vitamin that would do the same thing in non-superagers, so that people could extend their "middle age" for many years, Kim said.
None of the supercentenarians in the study had heart disease, stroke or diabetes — diseases that are very common in old age — and just one participant had been diagnosed with cancer. In contrast, in the United States, about half of people have been diagnosed with cancer by age 85, and 35 percent have been diagnosed with heart disease.
Unfortunately, the secret to a long life span remains a mystery for now — a first analysis of the genomes did not reveal any rare genetic mutations that might have been responsible for the participants' extraordinary ages. [Extending Life: 7 Ways to Live Past 100]
However, the researchers have made the genome sequences publically available in the hope that future research might discover secrets to their long life.
"The best way forward is for people to pool their data so we can compare all the supercentenarians," Kim said.
Previous studies have found certain variations in the genetic code of centenarians. But these variations, are also relatively common in the general population — for example, they might be found in 10 percent of people.
In the new study, the researchers hypothesized that people who live to be 110 or older may share a rare mutation, or a rare gene, that would be responsible for their long life, that was not common in the rest of the population.
The study was not able to find such a gene, but this may have been because there were too few people in the study to detect meaningful differences.
In addition, the genetic basis of life span is likely a complex trait — it could be that many small differences across a person's genome combine together to make for a long life span, Kim said. Or, it could be that, although there is no shared gene that is common among supercentenarians, individual families may each have their own gene for longevity, said Kim, who conducted the work with Stephen Coles, of the Gerontology Research Group in Los Angeles, Leroy Hood of the Institute for Systems Biology in Seattle, and colleagues.
The study is published today (Nov.12) in the journal PLOS ONE.