By around age 30, your body naturally begins to lose muscle mass and bone density, and at around age 40, your brain begins to lose volume to the tune of around 5 percent every decade. Some research suggests that our working memory — the ability to hold on to a piece of information like a password or street name — starts to decline in our thirties, according to BrainFacts.org.
But a new study from Colorado State University suggests that you may be able to turn back the tide of aging, at least when it comes to your brain. The study, published online June 24 in Neuroimage, found that participants who completed six months of regular brisk walks experienced better cardiovascular fitness and improvements in white matter and memory compared with people who practiced stretching and balance exercises for the same amount of time.
Can Exercise Help Prevent Dementia or Memory Loss?
Although this study isn’t the first to show that physical activity slows cognitive decline and even promotes positive changes in the brain (called neural plasticity), most of those studies, per a review published in December 2020 in Neural Plasticity, looked at gray matter, which makes up the outer layer of the brain and has a high concentration of neurons.
This new research focused on a less studied part of the brain called white matter, which is found in the deeper tissues of the brain and contains nerve fibers, which are extensions of neurons, according to MedlinePlus. Both white and gray matter are necessary for normal brain function.
It may be helpful to think of gray and white matter in terms of electricity, says Andrea Mendez Colmenares, a cognitive neuroscience PhD student at Colorado State University in Fort Collins, Colorado, and the lead author of the new study. “The light bulb is the gray matter, and all the internal electrical wires connecting it in your house are the white matter,” she explains.
Because white matter has been shown to degenerate in both healthy aging and dementia, it’s crucial to determine whether or not that process can be slowed or even reversed, according to the authors. Given the proven benefits of aerobic exercise on cognitive function, researchers decided to investigate if physical activity could promote positive changes in white matter.
Walking Was Associated With Improvements in White Matter, Memory
The study included a total of 247 participants who were older than 60, 68 percent female, and inactive but otherwise healthy adults with no history of neurological issues, such as dementia or stroke. Baseline measures on memory, processing skills, and cardiorespiratory fitness were taken at the start of the study, along with a special MRI brain scan to measure the health and function of white matter.
Participants were placed into groups and met three times a week for six months, with one group gathering for brisk 40-minute walks, one that participated in supervised stretching and balance training, and one that learned and practiced choreographed dances. At the end of the intervention, the brain tests and imaging were repeated.
Researchers found that the walkers and dancers had better overall cardiovascular health after six months of regular activity. While both groups had evidence of positive changes in the white matter, those changes were more prevalent among the walkers. MRI images revealed that certain parts of the brain appeared larger, and tissue lesions (a sign of damage to the brain) had shrunk. In the control group, there was a decline in white matter health.
“We think these findings are important because the regions we observed are sometimes vulnerable to aging or dementia. This tells us that the white matter is malleable, and even in regions that are susceptible to aging or disease you can still see a response to an exercise intervention,” says Colmenares.
The walking group was the only group where the changes in white matter were associated with better memory. It’s unclear why the dancers didn’t have those same improvements, though it could be because they were receiving instruction and not moving as vigorously during their sessions, according to the authors. This may mean that the effects of aerobic exercise were a primary driver of the white matter benefits.
One thing that sets this study apart is that it was a randomized controlled trial rather than an observational study, says Colmenares. Most trials that study the effects of exercise rely on participants reporting on the activities they are already doing, which can make the findings less reliable. “We actually performed an exercise intervention where these people came to walk, dance, or do balance training in a controlled environment,” she says.
What’s Good for Your Heart Is Good for Your Brain
This study wasn’t set up to discover why walking is good for white matter, but it is probably due to a combination of factors, says Colmenares. “Regular exercise that gets the heart beating faster is good for your heart, and what’s good for the heart is good for the brain,” she says.
Exercise can increase oxygen and blood flow to all parts of the body, including the brain, she explains. “This can improve blood pressure, which is important; high blood pressure is one of the most important risk factors for dementia and neurological disease,” she says. Regular physical activity is also associated with improved sleep and decreased stress, which could also have a positive impact on the brain, says Colmenares.