Several new genes linked to an exceptionally long life have been discovered, according to a new study that examined the genomes of people living into their 100s, known as centenarians.
Using a new method, the researchers found four genes linked with a very long life: A gene called ABO, which is involved in determining blood type; a gene called CDKN2B, which regulates cell division; a gene called APOE, which is linked with Alzheimer's disease; and a gene called SH2B3, which was previously found to extend life in fruit flies.
The researchers hope that future studies will uncover even more genes linked with longevity, and figure out how these genes may affect the aging process.
"There's a reasonably strong genetic component to becoming a centenarian, and we want to find out what that is," said study researcher Stuart Kim, a professor in the Department of Developmental Biology and Genetics at Sanford University. "We're beginning to unravel the mystery" of why some people age so successfully compared to the normal population, Kim said. [Extending Life: 7 Ways to Live Past 100]
Previous studies have attempted to find variations in genes that are more common in the very old compared with younger people, but haven't had much luck. These studies looked through millions of variations in the human genome, but they might have missed some important associations.
The new study aimed to narrow the search for genes linked with long life by focusing on ones that are known to strongly affect a person's risk of age-related disease, like heart disease and Alzheimer's. The thinking is that these diseases increase a person's risk of dying early, and so genetic variants that increase the risk of these diseases would also decrease the chances of a long life, the researchers said.
The researchers first searched for longevity-linked genes in a population of about 800 people over age 100 and 5,400 people over age 90.
They found eight genes that were linked with a long life span, and were able to confirm four of these genes in a follow-up analysis of about 1,000 people ages 100 or over.
The study found that certain variants in the ABO, CDKN2B, APOE and SH2B3 genes were more common in centenarians than in people with a typical life span. (Adults in the United States have an average life expectancy of about 79 years, according to the Centers for Disease Control and Prevention.)
For example, the study found that the a genetic variation associated with type O blood was more common in centenarians than in the study's control group, meaning that there were slightly more centenarians with type O blood, compared to people with a typical life span. Previous studies have found that people with type O blood have a lower risk of coronary heart disease and cancer, and have lower cholesterol levels than people with other blood types.
Another genetic variant in the CDKN2B gene seems to play a role in whether cells continue to divide, or stop dividing. Given that the stoppage of cell division, called senescence, is thought to contribute to aging, having a gene variation that reduces cell senescence could be a factor that contributes to successful aging, Kim said.
Kim suspects that there are still more genes linked with a longer life span.
"I hope our paper inspires other people to continue searching for" genes linked with longevity, Kim said.
The study was published yesterday (Dec. 17) in the journal PLOS Genetics.