May 21, 2018
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Can a blood test reveal how fast we’re aging?

By Thea Singer, Special to The Washington Post

As early as this fall, we may be able to get a simple blood test that can help us monitor not only our general health status but also how fast we’re aging — or at least how fast our cells are aging.

The test will measure the length of our telomeres, the caps on the ends of chromosomes that keep our DNA intact and our cells thriving.

News about the test’s imminent release has spurred a flurry of misleading reports suggesting that we’re on the cusp of being able to learn how long we’ll live — and whether we can ward off the irksome outward signs of aging. While scientists are divided over the value of the test for individuals, no serious researchers are saying a telomere test will be some kind of crystal ball.

At best, the new test represents another, more powerful tool among the tests already used to assess health — cholesterol, triglyceride and glucose measurements — not an entirely new approach. They aim to provide a one-stop snapshot of our statistical risk for everything from heart disease and diabetes to cognitive decline and mortality. If people can monitor their telomere length, the thinking goes, they can make lifestyle changes to alter that risk by boosting their cells’ longevity.

How can a simple test that analyzes white blood cells provide this kind of information?

When cells divide to replicate themselves, their telomeres shorten. That has led many scientists to view telomere length as a marker of biological aging, a molecular clock ticking off the cell’s life span, as well as an indicator of overall health. In general, older people have shorter telomeres than younger ones.

Ronald A. DePinho, a cancer biologist at Boston’s Dana-Farber Cancer Institute, recently proposed a unified theory of aging, with malfunctioning telomeres as what he called the “core pathway” causing health decline in advanced age.

But telomere length is just part of the picture.

“Telomere length, like any other risk measurement, tells us the probability of disease and early mortality. It is not a diagnosis,” stresses Elissa Epel, a health psychologist at the University of California at San Francisco and a founder of Telomere Health Inc., one of the companies making the test. “Telomere length is only helpful information when interpreted correctly, which is probabilistically.”

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