Walking approximately 6–9 miles a week is associated with increased gray matter in the brains of older adults. “Just by walking regularly, and so maintaining a little bit of moderate physical activity, you can reduce your likelihood of developing Alzheimer’s disease and [can] spare brain tissue,” Kirk I. Erickson, lead study author and assistant professor of psychology at University of Pittsburgh in Pennsylvania. The study participants were subjects in the Pittsburgh site of the larger Cardiovascular Health Cognition Study, a longitudinal study conducted over a 13-year period.
The Pitt researchers wanted to determine whether consistent moderate physical activity among older adults would be associated with cognitive health in later life. The scientists enrolled 299 adults with a mean age of 78 in 1989 and recorded the distance each person walked per week. Nine years after this measurement, investigators conducted MRI brain scans to measure brain size. At this stage, none of the participants exhibited any cognitive impairment. Four years later, approximately one-third of the subjects had experienced cognitive decline.
Data analysis showed that the individuals who walked a minimum of 6 miles per week had more gray-matter volume in the brain and only half the risk of developing cognitive impairment compared with less active subjects. Sections of the brain that retained more gray matter included the frontal and temporal brain regions, including the hippocampus and the entorhinal cortex. These brain regions can be subject to age-related deterioration. More gray matter in these areas is associated with reduced risk of developing dementia or mild cognitive impairment.
More physical activity, however, does not provide more benefits. “That’s because the size of our brain regions can only be so large,” said Erickson. However, the improvements that can occur are important: “What we often think of as an inevitable component or characteristic of aging—memory decline and brain decay—is clearly not inevitable. There’s plenty of evidence now . . . that shows that we can retain our brain tissue and retain our memories well into late adulthood by maintaining an active and engaged lifestyle.”