Long Life Is Imprinted in Genes of Centenarians

Mary McCarthy blows out the candles on her birthday cake with the help of her godson Elio Garcia at their home in Havana. A new study has identified a number of genes that are associated with extreme longevity in humans. REUTERS/Claudia Daut/Files

For some time, scientists have been trying to understand the reasons why some people live into their 80s, 90s and even 100s, and remain healthy, despite having lifestyle habits no different than those who live an average life span.

Part of that answer is hidden in DNA, according to a new study published Thursday in PLOS Genetics that identifies several genes that may explain longevity and why some people are much less predisposed to age-related chronic health conditions. Researchers at Stanford University and the University of Bologna have identified a number of genes and their loci—the specific location or position of a gene on a chromosome—that are associated with extreme aging.

"Longevity is a complex phenotype, and few genetic variants that affect lifespan have been identified," the researchers wrote in their study. "However, aging and disease are closely related, and a great deal is known about the genetic basis of disease risk."

The genes and their locations identified by the researchers included ones associated with Alzheimer's disease (APOE/TOMM40) and cancer cell proliferation (CDKN2B/ANRIL). Other gene loci that appear to be drivers behind longevity include ABO (associated with Type O blood group) and SH2B3/ ATXN2 (related to increased life span in fruit flies).

The researchers conducted an "informed genome-wide association study" (also known as iGWA), in which findings from several genome analyses are compared to spot similarities. They looked at existing data on 14 diseases and then used that information to narrow the search and seek out genes associated with longevity. The researchers used two existing iGWA studies of human longevity: the New England Centenarian Study (NECS), which includes 801 centenarians and 914 controls, and the 90PLUS study, which includes 5,406 elderly over age 90 and 15,112 controls. Then they replicated their findings with data from three additional centenarian cohorts from Southern Italy, Northern Italy and a pool of Ashkenazi Jews.

This study is the first to identify several gene loci associated with longevity. Previous research on human longevity has only isolated a single gene: APOE. In addition to Alzheimer's disease, APOE is also associated with cardiovascular disease.

Other longevity research has identified a number of trends in health of "super seniors" that are also driven by genetics. Some research has found that centenarians have HDL—good cholesterol—levels as much as two to three times higher than average, as well as slightly underactive thyroids and mutations that impact the production of certain hormones in the body.

Recent estimates from the U.S. census suggest there are some 55,000 people aged 100 or older in the U.S. (about 0.02 percent of the population). But longevity is becoming much more common. One study published in 2014 estimates there to be 317,000 centenarians worldwide, and that is projected to rise to about 18 million by the end of this century.