Memory is one of the most important functions of the brain. It is needed in all aspects of our lives. Unfortunately, a combination of genetic and environmental factors can deteriorate the memory and additional cognitive functions. A new neurodegenerative disorder case is diagnosed around the world every four seconds (Brinke et al., 2013). This means that by 2050, over 115 million people worldwide will have a form of dementia (Brinke et al., 2013). The most common condition is Alzheimer’s disease. Today, the world has 47.5 million people affected, including 747,000 Canadians (Alzheimer Society Canada, 2015). If nothing changes, that number will double to 1.4 million by 2031. Several studies confirm, however, that physical activity could beneficially decrease the risk of memory loss. Indeed, one in seven cases of Alzheimer’s disease could be avoided if sedentary individuals become more physically active (Zafar, 2013). According to a meta-analysis conducted in 2009, physical activity reduces the risk of developing Alzheimer’s disease by 45% (Hamer & Childa, 2009). This is possible through two ways: direct and indirect.
On one hand, physical activity directly stimulates the proliferation of growth factors. These are chemicals in the brain that are responsible for the growth of nerve cells and blood vessels supplying the hippocampus, the memory center (Brinke et al., 2013). According to an Alzheimer’s disease expert in Toronto, Dr. Tiffany Chow, exercise promotes the circulation of glucose and oxygen in the brain (Zafar, 2013). Therefore, physical activity will delay not only the onset of dementia in healthy individuals but also slow the decline of cognitive functions and reduce the mortality rate of people suffering from Alzheimer’s disease (Paillard, Rolland, Bareto & De Souto, 2015). Similarly, exercise is associated with an increase of blood flow in the brain, an increase in hippocampus size, as well as a high level of neurotrophic factors (or growth factors) in the plasma. These factors protect neurons from injury and/or disease.
On the other hand, physical activity can indirectly enhance memory and cognitive functions by improving our mood, sleep, and by reducing our anxiety (Brinke et al., 2013). In addition, rats that voluntarily run 10-15 kilometers for 24 hours have a higher score on spatial memory and learning tests compared to sedentary rats (Marosi & Mattson, 2013). Additionally, another study with human subjects who displayed moderate and severe cognitive impairment has shown that physical activity can improve memory (Scherder & Volkers, 2014). Not any type of exercise, however, can enhance brain activity.
Types of exercises
Aerobic exercises encourage hippocampus growth, particularly in regions responsible for verbal memory and learning, unlike muscle strength and balance activities which have very little impact on memory (Brinke et al., 2013). The Public Health Agency of Canada (2010) recommends 150 minutes per week of moderate to vigorous aerobic exercises. This may seem a lot for those who are sedentary but by increasing their performance regularly and by doing simple exercises, such as walking for at least one hour a day, they may accomplish the aforementioned recommendations. Several studies investigating brain memory also show the benefits of speed walking (Paillard, Rolland De Souto & Barreto, 2015). According to the same source, two factors increase the effect of physical activity on memory: socialization and motivation. Indeed, people who hold a conversation during speed walking are more successful on memory tests than those who walk alone. Likewise, rats running voluntarily (in other words, who had a high level of motivation) had better memory than those who were forced to run. Concerning the duration of aerobic exercices, one study shows the presence of cognitive benefits after only four weeks (Nouchi et al., 2013).
In summary, the link between physical activity and memory is undeniable. Exercise can directly increase brain growth factors, or indirectly enhance cognitive memory by improving mood and sleep. It also takes 150 minutes of aerobic exercise per week to maintain good mental health. This could have a big impact on public health since physical exercise is a cheaper alternative to expensive pharmacological interventions. It is clear that in addition to protecting against coronary heart disease, diabetes, high blood pressure, depression, and anxiety, physical activity also provides an advantage against neurodegenerative diseases. Thus, physical activity is perhaps not far from a panacea for all illnesses of the XXI century.
Alzheimer Society Canada (2015) Dementia numbers in Canada. Retrieved from http://www.alzheimer.ca/en/About-dementia/What-is-dementia/Dementia-numbers
Brinke, L. F. T., Bolandzadeh, N., Nagamatsu, L., Hsu, C. L., Davis, J. C., Miran-Khan, K., & Liu-Ambrose, T. (2013). Aerobic exercise increases hippocampal volume in older women with probable mild cognitive impairment: a 6-month randomised controlled trial. British Journal of Sports Medecine. doi:10.1136/bjsports-2013-093184
Hamer, M., & Childa, Y. (2009). Physical activity and risk of neurodegenerative disease: a systematic review of prospective evidence. Psychological Medicine, 39(1), 3-11. doi:10.1017/S0033291708003681
Paillard, T., Rolland, Y., & De Souto Barreto, P. (2015). Protective Effects of Physical Exercise in Alzheimer’s Disease and Parkinson’s Disease: A Narrative Review. Journal of Clinical Neurology, 11(3), 212-219. doi:10.3988/jcn.2015.11.3.212
Public Health Agency of Canada (2010) Chapter 3: The Health and Well-being of Canadian Seniors, The Chief Public Health Officer’s Report on The State of Public Health in Canada 2010. Retrieved from http://www.phac-aspc.gc.ca/cphorsphc-respcacsp/2010/fr-rc/cphorsphc-respcacsp-06-eng.php
Marosi, K., & Mattson, M. P. (2013). BDNF Mediates Adaptive Brain and Body Responses to Energetic Challenges. Trends in Endocrinology & Metabolism, 25(2), 89-98. doi: 10.1016/j.tem.2013.10.006
Nouchi, R., Taki, Y., Takeuchi, H., Sekiguchi, A., Hashizume, H., Nozama, T., Nouchi, H., & Kawashima, R. (2013). Four weeks of combination exercise training improved executive functions, episodic memory, and processing speed in healthy elderly people. doi: 10.1007/s11357-013-9588-x
Volkers, K. M., & Scherder, E. J. A. (2014). Physical Performance Is Associated with Working Memory in Older People with Mild to Severe Cognitive Impairment. BioMed Research International. doi:10.1155/2014/762986
Zafar, A. (2013). Alzheimer’s prevention strategy prescribes exercise. CBC News Health. Retrieved from http://www.cbc.ca/news/health/alzheimer-s-prevention-strategy-prescribes-exercise-1.1304156