Walk briskly to boost memory

By Dr. Ananya Mandal, MDFeb 1 2011

Researchers have found that older adults who took a brisk walk three times a week did better on memory tests and increased the size of their hippocampus, a portion of the brain involved with memory formation.

This means that age related loss of brain volume can be delayed, and may even be reversible. Brain shrinkage is associated with memory impairment in the elderly. Lead study author Kirk Erickson, an assistant professor of psychology at the University of Pittsburgh said, “We can change the brain in older adults… It’s amazing that a one-year period of moderate exercise isn’t just slowing down the atrophy, it’s actually reversing it.”

The team from the University of Pittsburgh, University of Illinois, Rice University and Ohio State University divided 120 sedentary adults in their mid to late 60s, on average, into two groups: one group walked around a track for 40 minutes of aerobic exercise, three days a week, while the other group (the control group) did stretching.

At the end of the study they noted that both groups performed better on a test of spatial memory. Spatial memory helps us to remember things like driving directions or where we left our keys. However on brain imaging by MRI scans at the end of one year the aerobic exercise group’s hippocampus was about 2 percent bigger than it was when they started, the equivalent to a reversal in age-related brain shrinkage of about one to two years, the researchers said. Those in the stretching group had a decrease of hippocampal volume of about 1.4 percent, the investigators noted.

Larger hippocampal volume was also associated with higher levels of brain-derived neurotrophic factor, a growth factor in the blood that is associated with brain health. Dr. Gary Kennedy, director of geriatric psychology at Montefiore Medical Center in New York City explained, “It’s very, very exciting and is essentially proving a theory that has been around for a while, which is that exercise can promote neurogenesis, or the transformation of neural stem cells in the brain into mature, functioning neurons…Exercise seems to enhance it or speed it up.”

It is possible that exercise could help ward off not only ordinary mental decline but also dementia, Erickson said. He added, “We really don’t have a good answer for that,” but prior research found that older people who walked between six and nine miles a week showed significantly less decrease in brain volume over nine years than couch potatoes, but walking more than that did not seem to increase brain volume any more.

Senior researcher Arthur Kramer, of the University of Illinois at Urbana-Champaign said, “With a limited investment of time and effort you can produce fairly dramatic improvements in memory and brain health… You can roll back the clock about two years.” Kramer said, “The brain is a complex place… A multitude of changes that happen as a faculty of aging reduces aspects of memory and cognition.”

Kramer added that the best part of the experiment is the simplicity of the exercise. He said, “Walking is simple and straightforward, and you don’t need to belong to a health club, though other forms of aerobic activities have similar effects.” “Those who exert more energy and do more activities tend to do better, tend to show a bigger improvement,” Erickson said.

“You don’t know what the increase is due to, in one trivial sense it could be just water,” Carl Cotman, director of the Institute for Brain Ageing and Dementia at the University of California at Irvine, who was not involved in the study said. “But if you translate the animal work it’s likely due to changes in neuronal structure and increased blood flow.”

Kramer said this could be true for other age groups like children as well. The study is published in its online version on Jan. 31 in the Proceedings of the National Academy of Sciences.