HEART
July 24, 2000

Going With The Flow

A new study shows that exercise can slow down the aging process for our blood vessels...

A 60- or 70-something with the veins and arteries of a 20-something?

A new study of young and aging athletes has shown that exercise can slow down the aging process for our blood vessels.

The researchers were surprised to find that the blood vessels of the older athlete group functioned just as well as either younger group.

Italian researchers led by Dr. Stefano Taddei of the University of Pisa studied the effects of exercise on blood vessels. Their study, published in the June issue of Circulation, the Journal of the American Heart Association looked at subjects in four lifestyle groups: 1) an older, sedentary group; 2) a younger sedentary group; 3) older athletes; and 4) younger athletes. Those selected for the athlete groups were long−distance runners, bicyclists and triathletes, who combine running, cycling and swimming. The younger groups averaged 27 years old, the older 63.

The researchers were surprised to find that the blood vessels of the older athlete group functioned just as well as either younger group. Evidence of the effects of the aging process, thought by many to be inexorable, were confined largely to the older,sedentary subjects.

"Long−term exercise protects the inner lining of the blood vessels from age−related changes and makes them behave more like those of a young person," said Dr. Taddei. Human blood vessels, when functioning properly, are able to widen in order to accommodate increases in blood flow. The key actor in this process is the endothelium, a layer of cells which serves as the inner lining of blood vessels. The endothelium produces nitric oxide, a substance that dilates, or expands, the blood vessels. Nitric oxide also protects the vessel walls from developing atherosclerosis — the accumulation of fatty substances that thickens the arteries and impedes blood flow — and thrombosis, or the formation of blood clots that can cause heart attack or stroke.

As we age, however, the endothelium gradually loses the ability to regulate nitric oxide production. This leads to changes in the endothelium that make older people prone to atherosclerosis and thrombosis.

The Doctor's Dr. John Morley, Dammert Professor of Gerontology, Saint Louis University Medical School and Director of the Geriatric Research Education and Clinical Center at the St. Louis V.A. Medical Center, cites nitric oxide production as the key to understanding the results of this study. "Nitric oxide plays a major role in aging," Morley says. "Inadequate amounts result in poor function of the blood vessels, increasing the risk of heart attack, impotence and stroke. Too much, however, can cause tissue destruction and accelerate the aging process." What exactly causes the ups and downs in nitric oxide production is not really known.

Another age−related change that affects endothelium function is an increase in the number of free radicals in the bloodstream. Free radicals are highly unstable oxygen molecules that cause damage to various tissues. They also play a major role in the formation of artery−blocking fatty deposits when they come in contact with LDL (so−called "bad" cholesterol). It is believed that exercise and certain antioxidant vitamins can protect the body by blocking free radicals.

The researchers in Dr. Taddei's study also found that older athletes had low blood levels of free radicals, as low as many of the younger subjects. Those in the older sedentary group had much higher levels of free radicals.

"It is exciting," Dr. Morley comments, "that the effects of regular exercise appear to include maintaining the production of nitric oxide and slowing down the aging process in our blood vessels. Once again, it appears that the best way to age successfully is to exercise regularly."

And while the athletes studied by Dr. Taddei were an extremely fit group, other studies have repeatedly shown that even moderate exercise can have tremendous benefits. For instance, recent research at the Honolulu Heart Program found that regularly walking more than 1.5 miles a day reduced heart disease risk in older individuals. "You do not need to be an athlete to get these beneficial effects from exercise," Taddei explained. "Aerobic activity five days a week — rather than intensive training — might just do the trick."

Reviewed by: John E. Morley, M.D.
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