Two new studies provide more evidence that regular aerobic exercise not only staves off the problems with thinking and memory that often come with age, but it can actually help turn back the clock on brain aging.

In one study, researchers found evidence that engaging in moderate physical activity such as brisk walking, swimming, or yoga in midlife or later may cut the risk of developing mild thinking problems.

In the other study, a group of elderly individuals who already had mild problems had improvements in their mental agility after six months of high-intensity aerobic activity.

People with mild mental impairments of the kind studied - known as mild cognitive impairment - typically have some memory difficulties, such as forgetting people’s names or misplacing items. Each year, 10 to 15 percent of individuals with mild cognitive impairment will develop dementia, as compared with 1 percent to 2 percent of the general population. Previous studies in animals and humans have suggested that exercise may improve thinking and memory.

To investigate further, Seattle-based researchers studied 33 adults with mild cognitive impairment. Twenty-three spent 45 to 60 minutes on a treadmill or stationary bicycle four days a week for six months, while the other 10 “control” subjects did stretching exercises but kept their heart rate low.

Six months of intense aerobic exercise “improved cognitive abilities of attention and concentration, organization, planning, and multi-tasking,” study chief Dr. Laura Baker noted in an email to Reuters Health. In contrast, cognitive function test scores continued to decline in the group that didn’t have vigorous exercise.

Might it be possible to get the same brain benefit from lower intensity aerobic exercise?

“In theory, yes,” Baker said, “but we are just now starting the studies that will help us know how little is enough. In the next five years, we’ll have a much better idea about the minimum ‘dose’ of exercise needed (how often, duration of exercise sessions, how much exertion is needed) without compromising the cognitive benefits.”

Baker, who is from the University of Washington School of Medicine and the Veterans Affairs Medical Center, Geriatric Research, Education, and Clinical Center, also noted that the average magnitude of mental improvement with aerobic exercise was “bigger for women than for men.”

And while she’s not exactly sure why, she noted that, for the women in the study, aerobic exercise improved the body’s sensitivity to insulin, a hormone that plays an important role in providing energy to the muscles and organs of the body and to the brain. “Contrary to our expectations, aerobic exercise did not improve insulin sensitivity for the men,” Baker said.

EXERCISE TO WARD OFF MENTAL DECLINE

The other study, by Dr. Yonas E. Geda and colleagues at Mayo Clinic in Rochester, Minnesota, involved 1,324 elderly adults free of dementia in 2006-2008. Experts determined that 198 had mild cognitive impairment and 1,126 had normal cognitive function.

Those who said they had engaged in moderate exercise such as brisk walking, aerobics, yoga, strength training or swimming in their 40s, 50s and beyond were less apt to have mild cognitive impairment, the researchers found.

Moderate exercise in midlife was associated with a 39 percent reduced likelihood of developing mild cognitive impairment, and moderate exercise in late life was associated with a 32 percent reduction in the odds of mental decline. The findings were consistent among men and women.

These two studies, both published in the Archives of Neurology, contribute to a growing body of literature supporting the benefits of a physically active lifestyle on the brain.

SOURCE: Archives of Neurology, January 2010.