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After being exposed to a virus, participants with shorter telomeres were more likely to catch the cold.

How likely are you to catch the next cold bug? The answer could lie in the length of your telomeres, according to a team of U.S. researchers.

Telomeres are protective caps on the ends of the 23 pairs of chromosomes that contain all our genetic material.

They are often compared to the plastic tips on the ends of shoelaces, preventing the chromosomes from fraying. Telomeres tend to get shorter as a cell undergoes normal division. Eventually, the telomeres become so short they can no longer hold the chromosomes intact and the cell dies. Aside from normal aging, telomeres can be cut short by other factors such as chronic stress or severe early childhood experiences. It's a bit like speeding up the body's biological clock.

Previous studies have found that seniors who have extremely short telomeres are at increased risk of cardiovascular disease, cancer and early death. But little is known about the role that telomeres play in the disease susceptibility of younger people. To find out, researchers at Carnegie Mellon University in Pittsburgh recruited 152 healthy volunteers, aged 18 to 55. At the start of the study, blood was drawn from each participant. From this sample, the researchers measured the length of telomeres in a particular type of white blood cell that helps the body fight infection.

Then each of the subjects was exposed to a common cold virus and kept in quarantine for five days, as the researchers observed which ones ended up getting sick. The finding, published this week in the Journal of the American Medical Association, showed that the participants with shorter telomeres were more likely to catch the cold.

This trend was clearly visible in those aged 22 to 55. But there was no relationship between telomere length and risk of infection among the youngest participates of the study, those aged 18 to 21. At this relatively young age, it seems there were just not enough immune cells with truncated telomeres to affect their susceptibility.

Still, the study found that telomere size certainly matters with increasing age.

"As the telomeres get shorter, the cell isn't functioning as well as it should," explained the lead researcher, Sheldon Cohen, who is a professor of psychology at Carnegie.

"And if a greater percentage of your [immune] cells are like this, then it means you are going to have fewer of them that are effectively fighting off the [cold] virus."

Although a lot more research needs to be done, Cohen said telomere length could be used to help predict a person's general susceptibility to disease.

It might, for instance, pinpoint those who are in need of special medical attention. And that raises another question: Can this susceptibility be reversed so that biology does not become destiny?

Scientists already know that an enzyme called telomerase protects telomeres from degradation. The key is to finding treatments, or activities, that boost the body's production of telomerase. One promising study has already indicated that regular exercise can raise overall levels of this protective enzyme.

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