NEW YORK (Reuters Health) – Staying physically fit with age may help protect people from mental decline by maintaining a healthy flow of blood to the brain, new research suggests.

A number of studies have found that regular exercise may help prevent or delay age-related cognitive decline and full-blown dementia, but the reasons are not fully clear.

For the new study, Canadian researchers looked at the relationships between physical fitness, brain blood flow and cognitive-test performance in 42 women between the ages of 50 and 90.

They found that those with the highest fitness levels generally showed better blood flow to the brain during exercise. This, in turn, was related to better scores on tests of memory, reasoning and other cognitive skills.

The findings are published in the journal Neurobiology of Aging.

“Our results suggest that the vascular benefits of exercise that have been reported previously in the heart and muscles are also conferred to the brain,” senior researcher Dr. Marc J. Poulin, of the University of Calgary in Alberta, told Reuters Health.

“Basic fitness — something as simple as getting out for a walk every day — is critical to staying mentally sharp and remaining healthy as we age,” said Poulin, who is also a scientist with the Alberta Heritage Foundation for Medical Research.

The study included 42 healthy postmenopausal women, some of whom regularly got aerobic exercise and some of whom were sedentary. All of the women took fitness tests on an exercise bike and had ultrasound scans to gauge their cerebral blood flow.

In general, fitter women showed better blood flow to the brain and greater responsiveness of the blood vessels to increased circulation.

“Our study identified strong and significant associations between physical fitness and cognition, and between physical fitness and vascular function in the brain,” Poulin explained.

This, according to the researcher, suggests that the benefits of exercise on mental function are at least partly explained by its effects on blood vessel function.

The results, Poulin said, “provide a strong scientific basis for future studies to examine how exercise improves cognition in older adults.”

“The implications are huge,” he added, “given the aging population and age-related diseases like Alzheimer’s disease and stroke.”

SOURCE: Neurobiology of Aging, January 2009.