Can This DNA Test Help Predict Your Longevity?

The Harvard Health Letter outlined the current view on the use of telomere length evaluation as a test of expected longevity.

There's no crystal ball in medicine that can predict how fast you're aging or how long you'll live. But the latest trend in private screening tests claims to provide a tantalizing clue. The tests offer a snapshot of the length of your telomeres — the protective caps at the ends of chromosomes in your cells.

"The concept is very attractive. There's this visual idea of something acting like a clock counting down to the end, and that's why it's powerful. The problem is that just because it's appealing it doesn't mean it's true," says Dr. William Hahn, a Harvard Medical School professor and chief research strategy officer at Harvard-affiliated Dana-Farber Cancer Institute.

About telomeres

Each cell in your body carries a set of genes, unique to you, that tell it what to do and when to do it. The genes (made up of DNA) are linked together in long strands called chromosomes. Chromosomes come in pairs: we have 23 pairs in each cell. At each end of each chromosome is a protective cap called a telomere, which keeps the chromosome from becoming damaged when a cell divides.

A telomere is made up of thousands of sections of expendable DNA. "Each time a cell divides, the telomeres shorten just a bit," explains Dr. Immaculata De Vivo, a Harvard Medical School professor and genetics researcher at the Dana-Farber/Harvard Cancer Center.

Once telomeres reach a critically short stage, they can't protect the chromosomes anymore, and the cell usually dies. Thus, the progressively shorter telomeres of a cell constitute a biomeasure of its aging.

Telomere shortening

How long are your telomeres at birth? And how much telomere length will you lose in a lifetime? "The answer to both questions is that it's different for everyone," notes Dr. De Vivo. "And the different rates of shortening depend on each person's genes and lifestyle."

Unhealthy lifestyle factors — such as smoking, eating junk food, obesity, inactivity, and chronic stress — are all associated with shorter telomeres. Shorter telomeres, in turn, are associated with a lower life expectancy and higher rates of developing chronic diseases, such as cardiovascular disease.

Telomere testing

Commercial telomere tests promise to uncover the status of your telomere length, claiming that this knowledge will reveal your "biological" age and help you make better lifestyle choices.

You can find telomere tests in several places. One is the Internet. For as little as $100, some companies will sell you a home kit that allows you to send your DNA (in a drop of blood or a cheek swab) to a lab. After a few weeks, the company mails you the test results, which tell you what your telomere length is and how that length compares to your peers.

For more money, you can talk to a company "coach," who explains the results to you and helps you come up with a plan for healthier living.

Other ways to get the test include

• ​​- going to a walk-in clinic with a doctor who'll order the test for you and then talk you through the results
• - buying and ordering a test from a company that directs you to a lab or a doctor who works in your area
• - asking your own physician to order the test for you.
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All of these options are more expensive than ordering a home kit, because you have to pay not just for the test, but also a doctor's time, and those prices depend on the particular office.

Is it accurate?

The accuracy of various commercial telomere tests is uncertain. There are few published methods for telomere measurements. There also is no government entity that oversees the accuracy of telomere tests. "There is no equivalent of the Food and Drug Administration, which monitors whether the pills you take really contain the medicine they are supposed to, and in the right dose," Dr. De Vivo says.

She also points out that a single telomere test — even when it is highly accurate — can't provide a true picture of biological aging or tell you how fast your telomeres are shortening. To determine that, you'd need a baseline test that's followed up over time with more tests.

How many tests would you need? "We in the research field have done testing intervals of one, three, five, and 10 years," Dr. De Vivo says. "For some people you can see a difference in three years. For some it's five years. It depends on the health status change of each person."

And it requires a physician to put the information into context with your medical history, Dr. De Vivo stresses.

Should you take action?

No matter what a telomere test finds, remember that scientists are still in the early stages of understanding what the information means. "If your telomeres are shortening, it doesn't mean something bad will happen. And if your telomeres are long, it also doesn't guarantee that something bad won't happen," says Dr. Hahn.

Yet all of the labs and clinics plugging telomere tests suggest that the results will help you make better lifestyle decisions to slow telomere shortening and increase telomere length.

Here are the facts: "There's nothing that has been proven to prevent the shortening of your telomeres," says Dr. Hahn. However, since stress and unhealthy lifestyle habits have been linked to shorter telomeres, it is reasonable to suppose that stress reduction and healthy habits might be beneficial. "There is mounting evidence that a healthy lifestyle buffers your telomeres," Dr. De Vivo says.

Learning your telomeres status could be a wake-up call to change behaviors associated with telomere shortening. You could eat a healthier diet, lose weight, stop smoking, or reduce stress.

But do you really need to pay for a test to tell you that?

"The value of a test to me is that it allows you to accurately predict what will happen and it indicates a course of action," says Dr. Hahn. "In this case, the test doesn't satisfy either one of those criteria."

Source: https://www.health.harvard.edu/staying-healthy/can-this-dna-test-help-predict-your-longevity