Published on: May 4, 2020
by Women’s Brain Health Initiative:
Your risk of developing dementia is influenced by a combination of genetic, environmental, and lifestyle factors. While there is nothing you can do about the genetics that you are born with, and there are only certain environmental factors that you can change, you do have complete control over the lifestyle choices that you make. It can be quite empowering to realize just how much of an impact lifestyle factors (particularly physical activity) have on your cognitive function and dementia risk.
There is a rapidly growing body of research suggesting that regular physical activity and/or high cardiorespiratory fitness level helps prevent cognitive impairment and lowers the risk of dementia.
In several studies, individuals with high cardiorespiratory fitness for their age have been found to have 36% to 88% lower risk of developing dementia compared to those who were unfit.
The findings from a study published in 2017 in Journal of Alzheimer’s Disease emphasize just how great a role physical activity plays in reducing dementia risk. That study, involving over 1,600 Canadians followed over a five-year period, found that sedentary older adults who have no genetic risk factor for dementia (i.e. are not carriers of the APOE e4 gene variant) may be just as likely to develop dementia as individuals who are genetically predisposed to the disease (i.e. are carriers of APOE e4).
“Our research revealed that inactivity dramatically increases the risk of dementia among non-carriers of APOE e4, so much so that it appears to completely negate any protective effects of having healthy, low-risk genes,” said Dr. Jennifer Heisz, an Assistant Professor at McMaster University and co-author of the study.
What’s the ideal exercise “prescription” for your brain?
There is extensive research suggesting that exercise is good for your brain. But there are lots of different ways that a person can exercise. Is there an ideal exercise “prescription” for maintaining cognitive function and preventing dementia? At this point, it is not clear what exercise regimen is best for your brain.
Determining an ideal exercise prescription for brain health is challenging because the study of physical activity and its benefits is very complex. There are many potential variables to consider, including:
Things are further complicated by elements of research design, which impact the strength of the results and how they can be interpreted. Do the researchers measure actual fitness level, or physical activity (and assume it is a reasonable indication of fitness)? Do they obtain their data about physical activity from self-reports by participants or from a device that directly measures movement? What measurement is used to determine fitness level or exercise intensity (e.g. heart rate or maximal oxygen uptake)?
Even though researchers cannot yet point to an ideal exercise prescription for brain health, there is a lot that they have discovered already.
Here are some highlights of what is known so far.
All types of movement seem to provide some level of brain benefit
Many studies over the years have pointed to the brain benefits of engaging in different types of exercise. For instance, various types of cardiovascular training and strength training appear to be beneficial. In past issues of Mind Over Matter®, we have covered the benefits of weight training (issue no. 4), dancing (issue no. 5), walking (issue no. 5), and even using balloons as a resistance training tool (issue no. 9).
Even a short exercise session offers benefits
Research has explored the benefits of exercise sessions of varying lengths.
One of the most important takeaway messages is that even short exercise sessions can give your brain a boost.
Issue no. 7 of Mind Over Matter® contains an article about how just ten minutes of exercise a day can make a difference.
Low-intensity exercise benefits the brain
In issue no. 9 of Mind Over Matter®, we shared some exciting research findings that showed that low-intensity exercise can have a positive impact on the brain and cognitive function. This was particularly good news for older individuals or those with health or mobility challenges that make it difficult to follow the Canadian Physical Activity Guidelines, which currently recommend engaging in moderate- to vigorous-intensity exercise.
Some research suggests high-intensity is best
While it is valuable to know that small amounts of light-intensity exercise can be beneficial for your brain health, it is also important to realize that higher levels of intensity have been found to be beneficial too, and perhaps even more beneficial.
Some studies suggest that engaging in high-intensity exercise yields the greatest benefit for cognitive health, compared with low-intensity exercise. For example:
Physical activity was assessed using an extensive questionnaire, and cognitive function was measured by a battery of neuropsychological tests.
In particular, higher intensity of weekly physical activity was found to be associated with better processing speed, memory, and mental flexibility, as well as overall cognitive function.
“The high-intensity interval training led to the greatest improvement in memory, boosting performance by up to 30% on average, while participants in the other two groups saw no improvement,” explained Dr. Heisz, co-author of the study. “Exercise intensity seemed to matter less for executive functioning, though, as we observed positive trends for executive functioning in both the high-intensity and moderate-intensity groups.”
Recent research conducted in Germany has revealed that physical activity performed at a level intense enough to have a beneficial effect on the heart and improve cardiovascular fitness results in positive changes to the brain itself. Dr. Katharina Wittfeld and colleagues evaluated the cardiovascular fitness of over 2,100 participants aged 21 to 84 between 2008 and 2012, and examined their brains using magnetic resonance imaging (MRI) scans.
The researchers found that higher cardiovascular fitness was associated with larger brain volume in several brain regions.
This research suggests that by exercising to improve cardiovascular fitness, you can possibly slow down the loss of grey matter volume that happens with age or disease, thereby improving your brain health.
One of the particularly exciting findings in this research was that the effect of improving cardiorespiratory fitness appeared to be stronger in individuals aged 45 years and older, suggesting it may never be too late to improve your brain health through exercise. These findings were published in the January 2020 issue of Mayo Clinic Proceedings.
Don’t overdo the intensity, though
Keep in mind that it is possible to overdo it when it comes to intensity. A review conducted by Dr. Jennifer Norman and colleagues published in 2018 in Current Pharmaceutical Design explains that while exercise has been shown to have beneficial effects on brain health, there can be adverse effects if that exercise is extreme or too vigorous (e.g. exercising to exhaustion or at a level far too high for your current level of fitness).
Perhaps moderation is key
Some researchers have found that it is moderate physical activity that improves cognitive function. It is possible that the relationship between physical activity and cognitive performance can be represented by an inverted U-shape, meaning that there is a sweet spot in the mid-range for physical activity where cognitive performance reaches a peak, but that as exercise moves away from that mid-point in either direction – in other words, moving toward very high intensity or very low intensity – cognitive performance diminishes.
How intensely should you exercise?
Given the current uncertainty about what level of exercise intensity is best for your brain health, what should you do?
It seems clear that moving your body in some way at any level of intensity (other than extremely high) benefits your brain and cognitive function.
You therefore should aim to do what you can, knowing that engaging in even small amounts of light-intensity exercise is better than being sedentary. However, if your health and mobility allow it, you might want to choose more vigorous activities that get your heart pumping to potentially boost the brain benefits.
“Keep in mind that what counts as high-intensity will vary for each individual and will change over time as a person becomes more or less fit,” explained Dr. Heisz. “Each person needs to choose exercise tailored to their current fitness level. And anyone starting a new fitness program or dramatically changing their exercise pattern should see their doctor first.”
Source: MIND OVER MATTER V10
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