The genetic clues to longevity may reside in DNA governing personality, say Brookhaven scientists who have searched the human genome to find out why some people live to great age.
Peter Thanos, a neuroscientist at Brookhaven National Laboratory, said scientists have asked for decades what it takes to reach the century mark: a specific genetic profile or the perfect environment.
He now thinks that he and his colleagues have found a major genetic hint.
Thanos and his team zeroed in on a personality-influencing gene tucked away in clusters of brain cells involved in dopamine activity. Dopamine is a neurotransmitter -- a brain chemical -- involved in a wide range of functions, including cognition, pleasure attention and the flow of hormones.
A derivative of the dopamine gene, discovered by Thanos and his colleagues and dubbed the DRD4/7R, is also involved in personality, he said.
"In people with this [gene] variant there is an association with the personality trait of impulsiveness," Thanos said.
He added that the gene is also linked to motivation and thrill-seeking behavior, traits would seem to counter the possibility of longevity.
But Thanos said the DRD4/7R is a marker for longevity because the people in their study who possessed it were all 90 years old or older.
The gene was not present in genetic samples from people who had died younger.
"We also found an association with exercise and protection from dementia," he said of the study's participants. "Overall they were more active and not just in terms of day-to-day activity but they were exercising -- walking, running -- being physically active."
The research involved 1,151 residents of Leisure World, a retirement community in Southern California.
But Dr. Gil Atzmon, director of a longevity project at the Albert Einstein College of Medicine in the Bronx, said no single gene tells the story of who lives longest -- or shortest. He wasn't involved in Thanos' research.
"It's not one gene," Atzmon said. "Longevity is a polygenetic trait. Multiple genes are involved. So now that another gene variant is introduced does that change things? No, not really."
Atzmon and his colleagues have already discovered eight genes linked to longevity, but he noted that genetics account for only 30 percent of why people live to 90 and beyond. The other 70 percent is environment, including the inner environment of the body itself, such as how well the heart beats or how well the body's micro chemical environment functions.
Atzmon and colleagues have studied hundreds of Ashkenazi Jews and found that people who reach 100 do not have lifestyles that are different from those die decades younger.
"They are overweight the same, they are obese the same, they smoked the same. No difference from the general population.
"Even if you don't have any of the favorable [genetic] variants, you can still make it to 100," Atzmon said. "Life expectancy in the West is increasing. In the United States it's now 80; in Japan it's 86, and in Monaco it's 89."
Also in the West, he added, life expectancy has been increasing by three months every year, which means in 10 years there will be nearly a 2.5-year addition to life expectancy.