Can Walking Reverse Brain Aging?

The brain is made up of white and gray matter. White matter connects different parts of the brain.
As we age, white matter deteriorates. White matter degeneration is even more severe in people with dementia.
Moderate aerobic walking three times a week can reverse age-related white matter impairments, as well as improve memory.

The brain is mainly made up of two types of substances: gray and white matter. White matter is made up of myelinated axons that connect different parts of the brain. They generate electrical signals and release chemicals to transmit information. As we age, white matter deteriorates; as a result, the signal becomes slower, misdirected, or lost. White matter degeneration is even more severe in people with cognitive impairment and/or dementia.

Because the global incidence of dementia is projected to double every 20 years [1], developing effective strategies to slow down cognitive decline—in both healthy and unhealthy brains—is critical. Learning about the brain pathologies that underlie age-related cognitive decline can help point scientists in the right direction. White matter deterioration, for example, leads to cortical “disconnection,” which is one of the main mechanisms of cognitive decline in healthy aging [2].

Fortunately, there is room for reclaiming white matter integrity even in our 60s and beyond. What's more, improvement or decline in brain health can occur in a relatively short time. One study showed that a decline in white matter integrity can occur over a short period of only six months in healthy older adults [3].

What We Know About White Matter in Aging Brains

There are some encouraging findings on the reversibility and the slowing down of age-related white matter shrinkage. In one study, Agnieszka Burzynska, a professor of neuroscience and human development at Colorado State University in Fort Collins, and colleagues collected brain images and cognitive measurements from a group of healthy sedentary men and women (60-79 years old; the average age was 65 years).

They randomly assigned participants to one of three conditions: walking, dancing, or active control [3]. Active control involved exercises designed to improve flexibility, strength, and balance with the aid of yoga mats and blocks, chairs, and resistance bands specifically designed for people 60 years of age or older. The walking intervention involved walking for 40 minutes at 60 to 75 percent of participants’ maximal heart rate. The dance condition involved choreographed dance combinations that became progressively more challenging over the course of the 6 months program.

Crucially, participants in all conditions attended three exercise sessions per week for 24 weeks (about 6 months). Researchers also measured the integrity of participants’ white matter using advanced neuroimaging parameters. Brain scans and all cognitive tests were repeated after the six-month exercise programs.

What the Research Found

All participants' bodies changed after completing the six-month exercise program. But did their brains change? The answer depends on what type of exercise was practiced.

Both the walking and dance interventions resulted in an increase in white matter and/or reduction in decline rate. However, the walking group showed more widespread positive effects as compared to either the dance group or the control group. What's more, the post-program improvements in white matter integrity correlated with improved memory only for the walking condition.

In other words, the dance intervention led to limited improvements in white matter and no impact on memory as compared to walking. And the participants in the walking group who showed the most white matter improvements also showed the most memory enhancements after completing the exercise program.

What this Means for Aging Brains

These results offer lots of hope. It is remarkable that age-related declines in white matter can be rescued after a brief period of moderate aerobic exercise training. It is equally important that these physiological changes led to noticeable improvements in memory function after only six months of exercising.

The results also beg the question: What happens to our brains if we do not engage in an aerobic intervention? Apparently, even six months of sedentary lifestyle can lead to an observable decline in white matter health. To understand how, let’s turn to the active control group in the study.

As a reminder, the active group was not completely sedentary! They engaged in exercises designed to improve flexibility, strength, and balance. Yet in this group, the authors observed a consistent pattern of decline in white matter over a period of six months for all white matter measured. Thus, the white matter deterioration was all over the brain for this control group. What's more, greater age was associated with a more negative change in white matter. It is sobering to learn that brain atrophy can be noticed within-person after just a few months.

This randomized controlled trial offers a compelling case for walking-related plasticity in humans over only six months. Note that participants in all conditions were healthy. One can imagine that unhealthy behaviors such as smoking, poor diet, and sleep deprivation, in addition to sub-optimal exercising—or no exercise at all!—would lead to earlier and more severe white matter impairments. Future research will have to confirm these conjectures.

For now, start walking today!

References

(1) Mayeaux, B., Stern, Y., (2012). Epidemiology of Alzheimer disease. Cold Spring Harb. Prespect. Med. 2. doi: 10.1101/cshperspect.a006239.

(2) Bartzokis, G., Sultzer, D., Lu, P.H., et al. (2004). Heterogeneous age-related breakdown of white matter structural integrity: Implications for cortical "disconnection" in aging and Alzheimer's disease. Neurobiol. Aging, 25, 843-851. doi: 10.1016/j.neurobiolaging.2003.09.005.

(3) Colmenares, A. M., Voss, M. W., Fanning, J., et al. (2021). White matter plasticity in healthy older adults: the effects of aerobic exercise. NeuroImage, 239, 118305.

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