How Does Exercise Protect Your Brain from Degeneration?

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I’ve been writing about the brain benefits of physical activity and cardiorespiratory fitness for over a decade. Every week, it seems there is new research that helps us better understand why exercise is so good for the brain.

Two new studies illustrate how regular exercise counteracts brain atrophy and degeneration. Hopefully, these findings will motivate you to stick with your current exercise routine—or to make a resolution to become more physically active starting today.

You don’t have to become an exercise fanatic to reap the brain benefits of moving your body. Moderate intensity aerobic activity—such as walking for 30 minutes most days of the week—can help protect your brain from shrinking and keep you sharp.

Exercise Increases Cerebral Cortex Thickness

The first study, conducted by researchers at the University of Maryland School of Public Health, found that exercise may help reverse neurodegeneration in both healthy adults and those with mild cognitive impairment (MCI).

Shrinkage of the outer layer of gray matter in the cerebrum—also known as the cerebral cortex—was found in both healthy older adults and those diagnosed with MCI. Improving someone's level of fitness increased the thickness of his or her cerebral cortex. The benefits of regular exercise and improved physical fitness were observed in both healthy older adults and those diagnosed with MCI, an early stage of Alzheimer's disease (AD).

The November 2015 study, “Improved Cardiorespiratory Fitness Is Associated with Increased Cortical Thickness in Mild Cognitive Impairment,” was published in the Journal of the International Neuropsychological Society.

For this study, participants (ages 61-88), who had been traditionally inactive, were put on an exercise regimen that included walking on a treadmill four times a week over a twelve-week period. Cardiorespiratory fitness improved by an average of about 8% as a result of the training, both in the healthy particpants and those with MCI.

Healthy brain (on the left) compared to brain atrophy observed in Alzheimer's disease (on the right).

Source: Public Domain/Wikimedia Commons

In a press release, Dr. J. Carson Smith, senior author of the study said, "Exercise may help to reverse neurodegeneration and the trend of brain shrinkage that we see in those with MCI and Alzheimer's. Many people think it is too late to intervene with exercise once a person shows symptoms of memory loss, but our data suggest that exercise may have a benefit in this early stage of cognitive decline."

Source: Public Domain/Wikimedia Commons

Smith and colleagues found that the study participants who had the greatest fitness improvement also had the most growth in the cortical layer. Both study groups showed strong associations between increased fitness and increased cortical thickness. This is the first study to show that physical exercise and improved levels of fitness can impact cortical thickness in older adults diagnosed with mild cognitive impairment.

In a previous study, Smith found that participants who walked for 30 minutes 3-4 days per week showed improvements in neural efficiency during memory recall and improved cognitive function. Other research he's published identified that moderate intensity physical activity protects brain health by thwarting the shrinkage of the hippocampus in older adults.

Exercise Triggers the Production of SIRT3

The second study, conducted by researchers at Johns Hopkins Medicine and the National Institute on Aging, found that exercise may energize brain cell function by producing an enzyme called SIRT3. The protective power of SIRT3 appeared to stave off neurodegenerative disease in mice who exercised regularly.

The November 2015 study, “Mitochondrial SIRT3 Mediates Adaptive Responses of Neurons to Exercise and Metabolic and Excitatory Challenges," was published in Cell Metabolism.

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As we age, our brain cells literally run out of gas in terms of their ability to produce sufficient energy to remain fully functional. The team of researchers led by Mark P. Mattson, Ph.D., of the National Institute on Aging Intramural Research Program and professor of neuroscience at Johns Hopkins University School of Medicine, used mice to investigate whether exercise could help neurons become immune to the energy-depleting stress caused by neurotoxins and other factors.

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The researchers found that mice who ran on a running wheel regularly created more SIRT3 in the mitochondria—which is most cell's central energy source. SIRT3 may protect the brain against the kinds of stressors and neurotoxins believed to contribute to energy loss and cell death.

Running wheel exercise increased the amount of SIRT3 in hippocampal neurons of normal mice and protected them against neurodegeneration. Mice who did not produce SIRT3 became highly sensitive to stress when exposed to neurotoxins that cause neurodegeneration and epileptic seizures.

These findings suggest that SIRT3 plays a pivotal role in the adaptive responses of neurons to physiological challenges and keeps them resistant to degeneration. Increasing SIRT3 levels through exercise may offer a promising therapeutic option for protecting against age-related cognitive decline and brain diseases.

Conclusion: Exercise May Help Maintain Self-Reliance As You Age

The million-dollar question is: Can moderate intensity physical activity help reverse or delay cognitive decline and allow individuals to remain independent and self-reliant as we age? I believe the answer is yes, but more research is needed.

Dr. Smith at the University of Maryland plans future studies that will include more participants engaging in a longer-term exercise intervention to see if greater improvements can be seen over time, and if these neuroprotective benefits persist over the long term.

The researchers at Johns Hopkins are hopeful that new methods for protecting neurons against stress through the use of a gene therapy technology that increases levels of SIRT3 could be developed based on their continuing research. Stay tuned!

If you'd like to read more on this topic, check out my Psychology Today blog posts,

• "Physical Activity Is the No. 1 Way to Keep Your Brain Young"
• "Better Brain Is Health Possible Without Exercise Fanaticism"
• "Why Does Physical Activity Improve Cognitive Flexibility?"
• "One Simple Way to Improve Your Brain Function"
• "7 Habits for a Healthy Mind in a Healthy Body"
• "Untreated Depression Linked to Telomeres, Aging, and Disease"
• "Emotional Distress Can Speed Up Cellular Aging"
• "The Brain Drain of Inactivity"
• "Very Small Amounts of Exercise Can Reap Huge Benefits"
• "One Thousand Reasons Breaking a Sweat Is the Best Medicine"
• "Why Does Physical Inactivity Drain Human Brain Power?"
• "How Could "Brain Observatories" Help the BRAIN Initiative?"
• "The Upward Spiral of Healthy Behaviors and Positive Emotions"
• “Making Exercise a Habit Prevents Age-Related “Brain Drain”"
• "Scientists Discover Why Exercise Makes You Smarter"

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