A Walk a Day Keeps the Brain OK

New research suggests that moderate exercise can keep brains sharp and focused.

Wrinkled skin and memory loss are just two of the annoying byproducts of aging. Some people fight wrinkles with Botox injections, but no such option exists for the more serious problem of cognitive decline. That could soon change; new research suggests that a stroll in the park might help iron out the mental wrinkles that accumulate as we age.

Numerous studies have hinted that elderly people who engage in regular exercise retain their mental agility longer than do their sedentary peers. But most of these trials did not assess directly the effects of physical activity, instead relying on seniors' recollection of their past attempts at keeping fit. Researchers therefore did not know whether exercise promotes mental oomph by protecting against memory loss or whether cognitive decline makes people less inclined to exercise. Now a two-part study--published last month in the Proceedings of the National Academy of Sciences--supports the former idea. The results provide the most direct evidence yet that exercise keeps people mentally focused throughout old age. If exercise turns out to nurture brainpower as well as this study suggests it does, then something as simple as walking could help keep elderly people out of nursing homes, boosting their quality of life and saving their families and Medicare countless dollars.

In the study's first arm, researchers measured the aerobic fitness of 41 healthy adults ages 59 to 79. They then administered a test in which the volunteers were asked to look at a collection of arrows and report which direction one particular arrow pointed. "The test measures the ability to focus in on specific information while excluding irrelevant information," says Arthur Kramer, a neuroscientist at the Beckman Institute at the University of Illinois, Urbana-Champaign. The fittest volunteers, Kramer and his colleagues found, could pick out the arrows' directions more efficiently than could participants who ranked poorest in cardiovascular fitness. Furthermore, functional magnetic resonance imaging (fMRI), a technique that measures the rate of blood flow to specific areas of the brain, showed that the highly fit participants displayed more activity in brain regions associated with attention than did the couch potatoes.

Kramer and his colleagues then took the study a step further with 29 healthy adults age 58 to 77. Participants in this part of the study were given the same initial tests as the first set of seniors were. But this time, the volunteers were split into two groups and assigned to a specific, supervised exercise program. One group performed light stretching, and the other group walked at a moderate pace three times per week. After 6 months, the researcher retested the participants on the fitness and arrow tests.

The results were dramatic. The walkers not only improved their cardiovascular fitness, they also improved significantly on the arrow test, boosting their scores by 11%, compared to the mere 2% improvement seen in those who stretched. Once more, fMRI showed that higher fitness levels correlated with more activity in the brain areas related to attention control.

"The theory that exercise might improve brain function is a pretty old idea, but it's only been recently that people have done the science to examine it," says Joe Verghese, a neurologist at Albert Einstein College of Medicine in New York City. A 2001 study compared exercise habits and cognitive function in more than 4500 adults enrolled in the Canadian Study of Health and Aging and found that physical activity was associated with a reduced risk of cognitive impairment and dementia. But Kramer's study is the first to place older adults on an exercise program and then ask whether it stoked their brainpower.

Exactly how exercise enhances attention skills isn't clear, but animal studies have shown that exercise increases the quantities of brain chemicals that help neurons connect. Exercise also boosts blood flow to the brain, which could keep the organ functioning optimally, says Kramer.

If further studies verify that exercise improves attention and other mental capacities, taking walks could provide an effective and affordable way for older folks to stay sharp. "We saw a significant performance improvement with exercise after just 6 months," Kramer says. What's more, "it's an intervention that's easy to implement."

The payoffs that Kramer saw in his trial should translate into improved performance in complex, real-life situations. Behind the wheel of an automobile, for example, "you're presented with a lot of information and you need to focus on the info that's most relevant, like a pedestrian stepping into the road," he says. Increased attentiveness would help the elderly in other ways as well, for example, decreasing the risk of falls, says Verghese.

At the same time, Verghese cautions against overextrapolating the results of this latest study. "We're still a few steps away from being able to recommend exercise as a dementia prevention," he says. Although Kramer's results are promising, Verghese notes that the study focused on only one very specific task and didn't include tests of memory.

Still, no one doubts that promoting exercise in older adults is a good idea. Regardless of whether exercise bolsters the brain directly, physical activity reduces the risk of several conditions that can drag down mental prowess, including high blood pressure and stroke. And the other advantages of exercise, such as improved cardiovascular health, weight control, and a reduced risk of depression and diabetes are well established.

But just as children turn up their noses at medicine that tastes bitter, adults might not take up exercise just because it's good for them. "You can create an intervention in the lab and it might work there, but out in the real world people are not going to do it unless it's something they enjoy," says Verghese. Fortunately, almost all people can find some kind of moderate exercise that they like, whether it's walking, tennis, golf, or bicycling. A daily workout might not be as easy as a Botox injection, but its potential rewards are far greater.

Christie Aschwanden is a freelance writer in Zuoz, Switzerland, who knows she would lose her mind if she stopped running.