A study of almost 1,000 people aged 100 or older has revealed 150 genetic variants that set centenarians apart from other people about three-quarters of the time, according to Dr. Thomas Perls of Boston University and colleagues.
In their report, published online in the journal Science, Perls and colleagues identified 19 clusters of genetic variants associated with exceptionally long life that correlated with the risk of developing age-related conditions such as dementia and high blood pressure.
The researchers noted that the average human lifespan in developed countries now ranges from 80 to 85 years.
"Environmental factors (lifestyle choices relating to diet, exercise, smoking habits, etc.) as well as genetic factors are believed to contribute to healthy aging," they wrote. "The results of human twin studies suggest that only 20-30 percent of the variation in survival to an age of about 85 years is determined by genetics."
So although environmental factors are involved, "genetics is playing a very important role in the wonderful trait," Perls told reporters in a telephone press conference.
Perls cautioned that the current study is not likely to lead to an "elixir" that could allow people to live to be 100 or more, largely because of the complex interactions among dozens of genetic variants that he and his colleagues found.
"This will not lead to treatments that will get a lot of people to become centenarians," he said, "but rather [will] make a dent in the onset of age-related diseases," although even that will require much more study.
Indeed, he said, the key to an extremely long life appears to be a capacity to delay the onset of age-related disability and diseases, such as cardiovascular disease, including stroke, and dementia.
"Centenarians are a model of healthy aging, as the onset of disability in these individuals is generally delayed until they are well into their mid-nineties," Perls and colleagues wrote.
In previous work, Perls and colleagues showed that 90 percent of centenarians live disability-free until age 93 on average. The few people who lived to be 110 or older, Perls added, were able to "compress both disability and disease even further" into the last years of their lives.
The current genome-wide association study gives some clues as to how these individuals might have been able to achieve that, according to lead author Paola Sebastiani, also of Boston University.
One possible explanation, she said, might be that centenarians had fewer genetic variants that predispose people to age-related illnesses. But a comparison of the prevalence of such "disease-associated variants" did not differ substantially between centenarians and controls, she said.
That suggests that the genetic variants associated with long life involve ways of overcoming the effects of disease-associated gene variants, she said.
About 15 percent of the controls also appear to have a "predisposition to exceptional longevity" based on the genetic model -- a proportion considerably higher than one centenarian in 6,000 observed in the general population.
That could be because the controls in this analysis are not a representative sample of the general population, Sebastiani said.