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Q: I read that shrinking chromosomes might be a sign of faster aging. Can a person be tested for this? Is there any way to slow that down?

A: The shrinking is actually happening in the telomeres, the protective caps at the ends of chromosomes in your cells.

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.

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 measure of its aging.

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.

Should you test your telomeres?

Commercial tests to uncover the status of your telomere length are available. But the accuracy of various commercial telomere tests is uncertain.

Also a single telomere test — even if it is accurate — can’t provide a true picture of biological aging or tell you how fast your telomeres are shortening.

No matter what a telomere test finds, 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.

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

But these are lifestyle choices you should make anyway, whether or not you have shorter telomeres.

Howard LeWine, M.D., is an internist at Brigham and Women’s Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, visit www.health.harvard.edu.
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