The Providence Journal - January 29, 2008

Research finds that those who are regularly active appear to have younger looking DNA.

As if gray hair, brittle bones and wrinkles weren't bad enough, scientists say that as you age, the very DNA in your trillions of cells starts to fray, unravel and disintegrate.

But now, they think there may be something you can do to slow the inevitable aging process - exercise.

A study published yesterday hints that fitness buffs appear to have "younger" DNA than the chronically sedentary. The finding could help scientists understand the effects of exercise and aging at a molecular level.

"These data suggest that the act of exercising may actually protect the body against the aging process," said Tim Spector, a professor of genetic epidemiology at King's College in London who led the study, published in the Archives of Internal Medicine.

Previous research has shown that being physically active reduces the risk of heart disease, cancer and other diseases, potentially extending longevity. In the hopes of helping explain how, Spector and his colleagues examined structures known as telomeres inside cells.

Telomeres cap the ends of chromosomes, the structures that carry genes. Every time a cell divides, the telomeres get shorter. When the telomeres get too short, the cell can no longer divide. Scientists believe that aging occurs as more and more cells reach the end of their telomeres and die - muscles weaken, skin wrinkles, eyesight and hearing fade, organs fail, and thinking clouds.

Not everyone's DNA ages at the same rate. Some people may start off with sturdier telomeres than others, or perhaps longer ones.

To try to separate the influences of heredity and lifestyle, Spector and his colleagues analyzed the telomeres from white blood cells collected from 2,401 twins participating in a long-term health study, examining whether there was a relationship between the subjects' telomere length and how much exercise they got in their spare time over a 10-year period.

"We're using telomere length as a marker of our rate of biological aging," Spector said.

The length of the twins' telomeres was directly related to their activity levels, the researchers found. People who did a moderate amount of exercise - about 100 minutes a week of activity such as tennis, swimming or running - had telomeres that on average looked like those of someone about five or six years younger than those who did the least - about 16 minutes a week. Those who did the most - doing about three hours a week of moderate to vigorous activity - had telomeres that appeared to be about nine years younger than those who did the least.

"There was a gradient," Spector said. "As the amount of exercise increased, the telomere length increased."

Other researchers said the findings are intriguing.

"It's another jigsaw piece in trying to understand why exercise is important in longevity," said Stephen Coles, who studies aging at the University of California at Los Angeles. But Coles and others stressed that much more research is needed to definitively establish a causal relationship between exercise and aging.

"It's a fairly strong association and a very interesting association," said Jack Guralnik of the National Institute on Aging, who wrote an editorial accompanying the research. "But we have to interpret this with caution. People who choose to exercise are different in many ways from people who don't exercise. It's always difficult from these observational studies to determine whether it's the exercise that's having the effects."

The study did not address what happens to the telomeres of people who are sedentary for many years and later begin exercising.

Previous research has shown that being physically active reduces the risk of heart disease, cancer and other diseases, potentially extending longevity. In the hopes of helping explain how, Spector and his colleagues examined structures known as telomeres inside cells.

Telomeres cap the ends of chromosomes, the structures that carry genes. Every time a cell divides, the telomeres get shorter. When the telomeres get too short, the cell can no longer divide. Scientists believe that aging occurs as more and more cells reach the end of their telomeres and die - muscles weaken, skin wrinkles, eyesight and hearing fade, organs fail, and thinking clouds.