If there were a medical test that could tell you whether you would live to 100, would you take it?
That's not the hypothetical question it once was. Scientists from Boston University are reporting they have a version of such a test.
Don't expect to see it on the market anytime soon. It's not 100 percent accurate -- and besides, what would you do with the information? But the researchers hope the tools they used to create the test will lead to a better understanding of the genetics of why some people live longer than others.
Searching For Longevity Genes
Geneticist Paola Sebastiani took DNA samples from participants in the New England Centenarian Study. All of the study participants lived to 100 or more.
Sebastiani looked for differences between DNA from the centenarians and the DNA of normal-aged people. As she reports in the journal Science, she was able develop a computer model that used 150 genetic markers, specific bits of DNA scattered around the 23 pairs of human chromosomes, to predict who would be able to join the centenarian club.
"The accuracy of this model is 77 percent," she says.
The model also allowed Sebastiani to identify genetic signatures: gene patterns that were present in subgroups of centenarians with particular characteristics. For example, the subgroup that lived the longest was also the group most likely to have delayed onset of diseases that typically affect older people: dementia, cardiovascular disease, hypertension.
In other words, Sebastiani says not only did these people live long lives; they lived long, healthy lives.
Test Is Not Ready For Prime Time
Sebastiani's co-author Thomas Perls says neither he nor Sebastiani has taken the test.
"Actually the various authors of the paper feel this isn't quite ready for prime time," says Perls.
Besides not being totally accurate, there's the question of what you would do with the information. He worries that people who found out they were unlikely to live to 100 might stop watching their weight or exercising.
Perls and Sebastiani agree that the real value of this study should be what it will tell scientists about the genetics of aging.
"At the moment this is a statistical analysis," says Sebastiani. "A lot of work still has to be done to then understand what is the biology, what is the contribution of all these genetic markers. So this is the first step."
More Experiments Are Needed
Geneticist Richard Myers of the Hudson Alpha Institute for Biotechnology in Huntsville, Ala., agrees. "It’s indicating experiments to do; it's not telling how you would use this to affect human health," he says.
And Myers warns that sometimes models based on statistics can steer you in the wrong direction.
"This is sort of the first hint of regions of the genome that might be important for extreme longevity. You have a hint, and that's better than having nothing," he says.
But it does mean understanding the genetics of longevity will take a while, maybe even 100 years. If we live that long.