exercise and dementia risk reduction

The Enduring Brain Health Benefits of Exercise

By Nicholas Chan | June 15th, 2020

More than 5.5 million people in the United States live with Alzheimer’s — one in every ten people over the age of 65. Knowing that her genetics increase her likelihood of developing Alzheimer’s herself as her father was diagnosed with the disease, Wendy Suzuki, a professor of neural science and psychology at New York University, decided to do what she could to maintain a healthy lifestyle: She exercises and socializes regularly, and maintains a healthy diet and sleep

While people’s genetics can increase their chances of developing dementia, scientific evidence continues to prove that lifestyle choices can reduce that risk or prolong the period of time before symptoms of neurodegenerative diseases like Alzheimer’s appear. 

In particular, a growing body of findings support the enduring benefits of exercise, especially for those who improve their fitness and heart and lung functions overtime. It can both help protect the brain from dementia, and it can reduce symptoms in people who already have it.

“It leads to changes in the brain’s anatomy, physiology and function,” Suzuki, whose research deals with Alzheimer’s prevention, told Being Patient. 

Evidence from animal and human studies shows that exercise may trigger a host of neurochemicals and the birth of neurons in the brain, improving mood, memory (even with just ten minutes of physical activity) and learning. Researchers say it’s never too late to start exercising, and that its benefits for brain health are enduring.

Being Patient takes a look at why that is, and what type and amount of exercise counts.

The Evidence 

To examine whether people who improve their fitness over time are less likely to develop dementia, researchers from Norway examined records of more than 30,000 people, categorizing them by the changes in their fitness levels. 

“We found that the improvement in cardiorespiratory fitness over ten years was strongly linked to lowering the risk of dementia,” said Atefe Tari, an author of the study and PhD Candidate at Cardiac Exercise Research Group at the Norwegian University of Science and Technology. 

Participants who were fit throughout the study were 40 to 50 percent less likely to develop dementia. Those who entered middle age out of shape but gained fitness were also at a lower risk. 

“It’s never too late to begin exercising. The average participant in our study was aged around 60,” Tari said. 

Exercise may also benefit people with mild cognitive impairment (MCI), those who may have the tendency to misplace things and trouble remembering the names of people they recently met. The American Academy of Neurology said that exercise could be the best prescription for MCI — and doctors should recommend it over medication. 

A study published last month provides further evidence of the benefits of exercise for those diagnosed with the condition which is a precursor to Alzheimer’s. 

Researchers conducted a year-long trial of people with mild cognitive impairment. 15 participants performed aerobic exercise while another 15 people stretched. Both groups trained 25 to 30 minutes three times a week. Over time, they increased the intensity and frequency of their training. 

“MCI is one of the earliest stages of Alzheimer’s that can be clinically diagnosed. Even at that stage, you can see improvement in memory and blood flow through the brain,” said Binu Thomas, an author of the study and a senior research scientist in neuroimaging at UT Southwestern. 

In particular, the group that performed aerobic exercise showed increased blood flow in the hippocampus and anterior cingulate cortex — the brain regions that play important roles in memory function. 

The Biological Link – What Exercise Does For The Brain?

While the hippocampus shrinks in late adulthood, exercise training may increase the volume of the hippocampus, a region of the brain key to regulating learning, memory and mood and one of the areas hit hardest by Alzheimer’s. 

Exercise boosts our mood and triggers a ‘neurochemical bath,’ Suzuki said. The brain releases the chemical messenger dopamine, which is involved with pleasure and reward. Increasing the blood flow to our brains, adrenaline shoots up and so too do the levels of serotonin, a chemical considered to be a natural mood stabilizer.

Exercise can even stimulate the birth of neurons in the hippocampus through the process of neurogenesis. The newborn neurons play crucial roles in memory functions and learning performance.

Even so, the number and maturation of new neurons involved in neurogenesis in the hippocampus of people with Alzheimer’s may decline. And scientists discovered in a mice study that the new neurons needed extra help to survive in brains with Alzheimer’s. 

“The stem cells were born in the battle zone of Alzheimer’s and they don’t survive,” said Rudy Tanzi, an author of the study and professor of neurology at Harvard University.  

Tanzi and other researchers found that exercise stimulated the production of a crucial molecule called brain-derived neurotrophic factor, or BDNF, that helped new cells thrive in mice with Alzheimer’s. 

In humans, there is evidence that exercise may increase levels of BDNF by two to three-fold. As people with Alzheimer’s, mild cognitive impairment and those who are aging may have lower levels of BDNF, exercise may be crucial to stimulating BDNF and research shows that the brain contributes to 70 to 80 percent of BDNF in circulation during exercise. 

The Challenges of Research in Human Brain and Exercise

Much less is known about how exercise may play a role in the neurogenesis and BNDF of human’s hippocampus. For one, it would be nearly impossible to track the development of neurons as scientists would have to harvest brain tissues postmortem. 

Even though researchers can detect levels of BDNF in blood samples, it’s much harder to pinpoint and quantify BDNF in a human’s hippocampus: Suzuki said some of the proteins are distributed to different areas of the body. And other parts of the brain may also induce BDNF. 

But one thing is for certain. “We absolutely know it in animal studies. We’ve known since the ‘90’s that an increase in exercise of rodents shoots up the level of BDNF in the hippocampus,” Suzuki said.  

Meanwhile, exercise can also boost the functions of the prefrontal cortex, enhancing our ability to store temporary information, crucial for maintaining our working memory. While more research needs to be done to understand the biological mechanisms, “the bottom line is that improved function of the prefrontal cortex is one of the most common findings in human behavioral studies of exercise,” Suzuki said. 

But researchers still face many obstacles in studying how exercise may improve the functions of the prefrontal cortex. Suzuki noted that the majority of studies have focused on the hippocampus.

“The rat has a huge hippocampus. They’re easy to study” Suzuki said. “The prefrontal cortex of a rat and a mouse are tiny. They are there and there are plenty of people who study it. But it’s more challenging.” 

While researchers can conduct brain scans to detect changes in the prefrontal cortex, Suzuki said it still won’t show scientists the molecular and chemical pathways that may trigger such changes in humans after exercise. 

“That’s why we use animal studies. That is the value and power of animal studies despite the fact that the prefrontal cortex [of rats] is smaller. They don’t have the same brain capacity. Yet, they have a model system,” Suzuki said. 

Meanwhile, human studies also show that exercise can boost the activity of a region in the prefrontal cortex and may improve mental focus

Motivating your loved one to exercise 

Motivating a loved one to exercise may be a challenge for some caregivers. Suzuki suggested that caregivers can play music as a source of encouragement, tunes that their loved ones with dementia enjoy. 

After all, music can transform those with dementia who are withdrawn into a more joyful state, reducing their agitation and even improving the mood of caregivers. 

Caregivers should also be open to a variety of exercises. Don’t be afraid to start with a simple exercise routine such as taking them on a walk around the grocery store: “If you are trying to motivate your mother or father with dementia, that counts as exercise. Make sure you’re not too strict in your own definition of exercise,” Suzuki said. 

To improve heart and lung functions, Tari recommends working out three times a week, breaking sweat, and increasing your pulse at intervals. 

“Get your heart rate up to when it’s hard to complete a sentence,” Tari said. 

While Suzuki said it’s likely more beneficial for older adults to get their heart rate up at intervals, it is much more difficult to stick to an intense routine for older adults who are unfit. 

“An older person can have demonstrable benefits of staving off dementia with walking,” Suzuki said. “Why is that? Again we’re not sure of the mechanisms … but studies have certainly shown that walking for older people can be very effective for brain health.”

And walking is the first step to building up the intensity of people’s exercise routine overtime.

It’s important to ensure your loved one with dementia understands the benefits to their brain health, Suzuki added, especially its ability to improve their mood. She reminded caregivers of an important point: “You’re trying to create an enjoyable experience for them.”


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