Medical Perspectives | Cardio-Metabolic

September 29, 2020



Dr. Stacy Dana D. San Diego, MD

            During Medical School, I had to rely on my memory and cognition to pass all exams. I tried a few tricks to survive which included listening to classical music; drinking energy drinks infused with Gingkgobiloba; and turning the pages of my study material into the most colorful and messiest piece of paper. I have tried everything except studying in advance because I am a notorious crammer. Studies have shown that if you want to improve your memory, you might want to exercise.   

            What makes a good memory? Is it being able to study for countless of hours and do well in exams or is it being able to recall the mundane details of our day to day lives? We have always thought that good memory is a product of good genetics, natural talent, and sometimes, of supplementation. Our memories are like our own little library of personal experiences and collected knowledge. These memories shape us into the persons that we are today. But what happens when a person suddenly or gradually loses them?

            Dementia is a syndrome in which there is deterioration in memory, thinking, behavior, and the ability to perform everyday activities. Worldwide, around 50 million people have dementia, and there are nearly 10 million new cases every year (WHO). Being forgetful is common among the older population but Dementia is not. Some studies have shown a relationship between the development of cognitive impairment and inactivity and life-style related risk factors which predisposes an individual to develop dementia.

The Harvard Health Publishing in November 2016recommended exercising that gets your heart rate up or any moderate intensity exercise for 120 to 150 minutes per week to improve our memory and thinking skills. Exercise has been proven to have numerous health benefits but sadly, these benefits outweigh the majority’s preference to lay and watch TV series. We have always associated exercise with aesthetics and cardiovascular health. Let us be honest, most of us will only exercise to lose weight and not to have a good healthy heart. If the public gets educated more about exercise, especially on its benefits in improving our cognitive skills and memory, then more will dedicate a few minutes of their time to get moving.

            A 2017 research published in the American Journal of Health Promotion studied 88 college students who exercised prior to memory encoding, exercised during encoding, exercised during memory consolidation, and a group who relaxed in all phases of activity. The exercise stimulus consisted of a 15 minute moderate intensity walk on a treadmill. The results showed that those who exercised before encoding did better than the rest of the groups. Long term memory was also assessed after 24 hours and the group who exercised prior the memory encoding and consolidation performed better.                     

            The effects of exercise in terms neurological activity in quantitative factors were also assessed. A 2016 study in Neural Plasticity, measured BDNF (brain derived neurotrophic factor) and cortisol which are mediators associated with learning and memory changes. BDNF is essential in the formation and storage of long term memories. Exercise has been shown to increase the expression of BDNF in the brain. Exercise can be also considered as a physical stressor hence, can increase the levels of cortisol, a stress hormone. It is known that glucocorticoids or in this case, cortisol, enhance memory consolidation. In this study, 81 students either relaxed or performed low and moderate intensity exercise after memory encoding. Memory recall was better for the relaxing group but after 24 hours, the students who engaged in a high intensity exercise did not forget the learned activity. Moreover, serum BDNF and cortisol were both significantly increased in the high intensity exercise group.

            As we age, the total volume of our brain shrinks. The hippocampus is part of the limbic system which is associated mainly with memory, in particular long-term memory and also spatial navigation. Hippocampal volume shrinks 1–2% annually in older adults without dementia. Damage to the hippocampus can lead to loss of memory and difficulty in establishing new memories. In Alzheimer Disease, the hippocampus is one of the first regions of the brain to be affected.

            A 2011 study had 120 older adults as participants who either did moderate intensity aerobic activity 3 times a week or stretching and toning exercises for 1 year. Results showed aerobic exercise training increases the size of the anterior hippocampus, leading to improvements in spatial memory. Exercise training increased hippocampal volume by 2%, effectively reversing age-related loss in volume by 1 to 2 years. It also demonstrated that increased hippocampal volume is associated with greater serum levels of BDNF.

            There are numerous studies on exercise and its correlation to memory and cognition. These studies had different objectives and methodologies and showed different results. Nonetheless, the findings of the studies all point to one thing which is the improvement of brain power. If everyone hadknown this back in medical school, then everyone could have avoided those dreadful added pounds and have passed with flying colors.

 

References:

Exercise training increases size of hippocampus and improves memory: http://www.pnas.org/content/108/7/3017

Temporal Effects of Acute Walking Exercise on Learning and Memory Function: http://journals.sagepub.com/doi/abs/10.1177/0890117117749476?journalCode=ahpa

Regular exercise changes the brain to improve memory, thinking skills: https://www.health.harvard.edu/blog/regular-exercise-changes-brain-improve-memory-thinking-skills-201404097110

The Effects of Acute Physical Exercise on Memory, Peripheral BDNF, and Cortisol in Young Adults: https://www.hindawi.com/journals/np/2016/6860573/

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