A genetic test that can predict whether a person is likely to live long enough to see their 100th birthday has been developed by scientists.
Researchers at Boston University in the United States claim the test can identify those who can look forward to an exceptionally long life with 77% accuracy. They designed the test after a major study into the genetic makeup of centenarians highlighted a host of DNA variants that boost a person’s chances of reaching a ripe old age.
Many of the genetic markers the scientists found stave off common, and often lethal, age-related diseases such as heart disease, dementia and high blood pressure. The US researchers investigated the genetic secrets of a longer life after studies showed that living beyond 100 often runs in families.
“These families might share healthy lifestyles, but it also suggests there is a strong genetic background to exceptional longevity,” said Professor Paola Sebastiani, a biostatistician at Boston University’s school for public health. Lifespan is governed by a complex interplay of genes, lifestyle and environment, with factors such as smoking, diet, exercise and pollution all having a role.
But many scientists believe living beyond the mid-90s is largely down to having good genes. Sebastiani and colleagues scanned the genomes of 1 055 centenarians and compared them with scans from 1 267 normal, healthy people. They found 150 DNA variants that were more common in the old-aged group and seemed to make their bodies healthier and more resilient.
The centenarians could be divided into 19 groups based on their genetic make-up. One of these groups was particularly resistant to age-related diseases and contained nearly half of all the centenarians that lived to 110 years or more. “There are particular combinations of these genetic variants that allow people to live not only a longer life, but also a healthier life. In centenarians, disability and disease tend to be delayed until the very end of their lives,” Sebastiani said.
The study, published in Science, will help researchers unravel why and how the body ages and could lead to drugs that can slow down the ageing process. “If we can pinpoint genetic variants that delay the onset of diseases, it could have very important medical implications for the population in general,” said Sebastiani.
One intriguing finding in the study was that gene variants that raise a person’s risk of disease may matter less than genes that protect against disease. The scientists found that centenarians had roughly the same number of highrisk genes as the rest of the population, but had more protective genes.
The finding is important, because commercial genetic tests look only for genes that raise a person’s disease risk, rather than reduce it. The study looked only at Caucasians, but Sebastiani said scientists should now look for DNA markers of longevity in other population groups.
Jeffrey Barrettt, an expert on disease genetics at the Wellcome Trust’s Sanger Institute in England, said the test might turn out to be less accurate when it is independently verified. “Some of the genetic variants in this study are claimed to have much, much stronger effects on longevity than we’ve seen in similar studies of diabetes, heart disease and cancer,” he said.
“For instance, the strongest single effect makes someone 10 times more likely than average to be extremely longlived, compared to other complex diseases where typical variants only make someone, say, one-and- a-half times as likely to be diabetic.
“Subtle biases in their work could contribute to these surprisingly large effects, which would make the test seem more accurate than it really is. Evaluation of the test by an independent laboratory will be the ultimate test of its accuracy,” Barrett said. —