How To Keep Your Aging Brain Fit

by Sharon Begley

The key to keeping intellectually sharp as we age may not be mental gymnastics, as commonly recommended, but real gymnastics.

According to a new study, the brain's long, slow decline may not be inevitable. For the first time, scientists have found something that not only halts the brain shrinkage that starts in a person's 40s, especially in regions responsible for memory and higher cognition, but actually reverses it: aerobic exercise. As little as three hours a week of brisk walking -- no Stairmaster required -- apparently increases blood flow to the brain and triggers biochemical changes that increase production of new brain neurons.

As brains age, normal wear and tear starting in middle age causes them to process information more slowly, which means it takes longer to make judgments and grasp complex information. Older brains also take longer to switch from one task to another and are less adept at "multitasking" (such as driving while simultaneously tuning the radio and checking the tailgater).

The search for ways to slow down mental decline and detrimental brain changes that come with age has taken an unexpected turn lately. Popular wisdom, as well as some scientists, had long held that the way to stay mentally sharp was to do mental gymnastics. Crossword puzzles, reading, taking up a musical instrument, and generally challenging the mind were supposed to stave off the mental ravages of old age.

That has been hard to prove. But support for the brain benefits of physical exercise has become stronger. A number of earlier studies showed that elderly people who take up aerobic exercise show improved cognitive function after a few months, says Arthur Kramer of the University of Illinois, Urbana: Their working memory is better, they are nimbler at switching between mental tasks, and they can screen out distractions better than people who did not get exercise training.

Now he and colleagues have discovered what may be the basis for these improvements. As little as three hours a week of aerobic exercise increased the brain's volume of gray matter (actual neurons) and white matter (connections between neurons), they report in the November issue of the Journal of Gerontology: Medical Sciences. "After only three months," says Prof. Kramer, "the people who exercised had the brain volumes of people three years younger."

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