Do Genes Determine Who Lives to Be 100 or More?
There's been a lot of controversy lately about a study published in the journal Science by a group of Boston University researchers who say they've been able to identify about 150 genetic variations that predict longevity.
If they are correct, a test based on those markers could predict who is most likely to have a long life and who isn't, all other factors being equal. Is the study valid? And if it is, does that mean how long you live is mostly predestined from birth, and that how you live doesn't matter as much?
The BU scientists, who studied 1,050 centenarians and 1,267 control subjects in New England. report that 90 percent of the centenarians fit into various clusters of the 150 genetic variations, which are linked to Alzheimer's, hypertension and 17 other age-related diseases. They maintain that the model they created is able to predict a long lifespan with a 77 percent accuracy. The team found that the oldest subjects--those 110 or older--had genetic signatures with the highest proportion of longevity-associated genetic variations.
Since the study was released July 1, however, critics have attacked the sample size and the genetic analysis methods, saying they undermine the credibility of the findings. "I think it is very unlikely indeed that the findings in the Science paper are correct, or even mostly correct," Duke University geneticist David B. Goldstein told The New York Times. Here's a blog post from the science publication Nature that goes into the details.
Perhaps the big problem with the study is how it has been misinterpreted by some in the nonscientific news media. The headline of this AOL Health story, for example, proclaims that seniors with the right genes are "The Chosen Ones" and quotes an endocrinologist saying that the study confirmed that genetics are "most important" in determining who lives longest. However, as the BU researchers themselves noted in their paper in Science, that is not the case. To the contrary, they write, previous studies of twins have indicated that only 20 to 30 percent of their longevity to age 85 is due to genetics. As Science News correctly reported,
Environmental factors, including lifestyle choices such as diet, smoking and exercise habits, are still the most important determinants of longevity.
Additionally, the researchers' findings, if accurate, indicate that there is no one genetic path for reaching ripe old age. Instead, the study identified as many as 19 different genetic combinations that might help a person to get there. That suggests that the explanation for longevity is probably a lot more complicated than we ever suspected.
Meanwhile, data gathered by Germany's Max Planck Institute for Demographic Research on "supercentenarians"--that is, people who live to 110 or older--indicates that, whatever the explanation, there seem to be more of them than ever, and they tend to have an astonishing vigor well into their 9th and 10th decades. The study found no strong correlation between living long and having long-lived ancestors, which tends to undermine any argument that longevity is largely genetic. Indeed, ancestry was no more important a factor than whether a person had offspring. Additionally, the survey showed that supercentenarians didn't have any magical immunity to disease. Indeed, some were cancer survivors. The one exception: Almost all of them didn't develop dementia, or at least avoided it until just before their deaths.
The researchers, who spent the past decade searching for supercentenarians, found about 600 of them worldwide, including 20 people who lived past 115. More than half of the super-centenarians--341 people--lived in the United States. The oldest person in the study was a French woman, Jeanne Calment, who died in 1997 at the age of 122. (She recalled meeting Vincent Van Gogh when she was 13.) When interviewed at 120, Calment said she believed that the secret of her long life was "fun" and that she enjoyed pleasurable things in moderation. She liked good food, wine, cakes and chocolate, and allowed herself one glass of port and one cigarette per day.
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