Posted on by Meredith Luttrell

The Importance of Aerobic Exercise on the Aging Brain

Author: Ian Malaby

Introduction

            As the world and technology advances, the average daily life becomes easier, and the average human being becomes more sedentary with an overall decline in physical activity11. Our bodies change a lot as we age, on large and small scales. Healthy measures should be taken in order to increase ones lifespan. This majorly includes physical exercise, specifically aerobic. Aerobic exercise, or exercise that requires the breathing of oxygen is essential to maintain not only bone, muscle, and cardiovascular health but also preserve the brain and nervous system. Aerobic exercise increases the blood and oxygen flow to the brain, which positively affects the brain and its associated structures and molecules.  

BDNF, Neurogenesis, and Neuroplasticity

Brain-derived neurotrophic factor (BDNF) is one of the many neuron (nerve cells) supporting factors in the nervous system. BDNF supports the growth, maturation, and survival of neurons as well as a major role in energy balance. BDNF is found in most areas of the brain including the cortex (processing, senses, motor function), hippocampus (memory formation), hypothalamus (hormone release), brainstem (homeostasis), and spinal cord1. Fortunately, an increase in BDNF also increases the rate of neurogenesis and neuroplasticity in the brain. Consequentially, a low amount of BDNF is shown in cases of depression and Alzheimer’s disease.

Neurogenesis, or the creation of new nerve cells (neurons) is a process that occurs throughout life. Adult neurogenesis can be caused by many physical stimuli; one of them being physical exercise. In contrast, aging leads to a significant decrease in the production of new neurons6. The amount of neurogenesis that one’s brain goes through in their adult life may also be determined by genetics. However, as stated earlier, is not the only factor contributing to the generation of new neurons in the brain4.

Neuroplasticity is the capacity of the nervous system to modify its organization. Tasks 

that we do more often, we become stronger at and the parts that we do not use fade away. Contrary to popular belief, connections in the brain are constantly forming as we age, and aerobic exercise can help form those new connections. It was once thought that when a nerve died there was no way to repair it or grow more. This has now been proven to be outdated based on the principles nerve growth and maintenance. Neuroplasticity can even be seen within short timescales8, meaning short bouts of aerobic exercise can strengthen the neurons in our brain. 

Brain and Aging

            Aging is associated with changes throughout the entire human body. Not only does aging have detrimental effects to our muscles and bones, but it also has these effects on the nervous system. The brain changes anatomically and functionally as we age, usually resulting in a cognitive/intellectual decline. The network of neurons that are formed in the human brain throughout the lifespan tends to get weaker and develops at a slower rate. This decline in function is not uniform throughout the brain with the most affected regions being the frontal cortex (emotion, problem solving, memory) and temporal cortex (sound processing)9. Studies have shown that there is a decrease in BDNF as we age, which is possibly one of the contributing factors to age-related cognitive impairments. Additionally, many life-style factors can affect how successfully the brain ages. These factors can include: number of calories ingested, quality of diet, active social life, proficient stress maintenance, and physical exercise7. 

Aerobic Exercise Altering Brain Structure and Function

            There are numerous health benefits to exercise, including disease prevention, strengthening muscles and bones, and also improving brain functioning. It is possible to improve cognition just with short-term aerobic exercise. A study done by Chapman3 and colleagues found that blood flow to the brain and cognitive abilities (memory recall) were seen in participants who had gone through short-term aerobic exercise sessions compared to a control group. This would suggest that even short bouts of aerobic exercise can facilitate the retention of neurons in the brain as one ages. Another study done by Tsai10 and colleagues looked at reaction times and BDNF levels after acute aerobic exercise. The results showed a decrease in reaction time, as well as an increase in BDNF levels. However, these results may be fitness-dependent meaning the more ‘fit’ an individual is, the better the results. With prolonged aerobic activity an increase in hippocampal volume is shown compared to baseline values. In older adults, a larger hippocampus is related to better memory whereas the opposite is seen in children and young adults. Increasing this volume can prevent against depression, alzheimers, and post-traumatic stress disorder. This could be due to the increased generation of new neurons and blood vessels in the brain via increased oxygen flow from exercise5. Another outcome of increased BDNF levels via exercise is an improvement in depression symptoms1.Along with aerobic exercise, cognitive exercises also show substantial training gains in the brain. Aerobic exercise was shown to lead to more efficient conflict monitoring and overall behavioral improvements2. 

Conclusions

            Aging adversely affects the overall health of the human brain, however with positive lifestyle choices these changes can be reduced. With regular aerobic exercise and other healthy lifestyle choices, the human brain can be protected against detrimental effects. BDNF levels increase with aerobic exercise, which in turn increases the levels of neurogenesis and neuroplasticity. Cognitive functionality takes a severe toll with the aging process but this can be postponed as stated earlier. If one is worried about their brain function and health as they age, simply suggest aerobic exercise to get the nervous system up and moving.

Citations

  1. Bathina, Siresha, and Undurti N Das. “Brain-Derived Neurotrophic Factor and Its Clinical Implications.” Archives of Medical Science : AMS, Termedia Publishing House, 10 Dec. 2015, www.ncbi.nlm.nih.gov/pmc/articles/PMC4697050/.
  2. Brehmer, Y., Kalpouzos, G., Wenger, E. et al. Psychological Research (2014) 78: 790. https://doi.org/10.1007/s00426-014-0587-z
  3. Chapman, Sandra B., et al. “Shorter Term Aerobic Exercise Improves Brain, Cognition, and Cardiovascular Fitness in Aging.” Frontiers in Aging Neuroscience, vol. 5, 2013, doi:10.3389/fnagi.2013.00075.
  4. Kempermann, Gerd. “Activity Dependency and Aging in the Regulation of Adult Neurogenesis.” Cold Spring Harbor perspectives in biology vol. 7,11 a018929. 2 Nov. 2015, doi:10.1101/cshperspect.a018929
  5. Jonasson, Lars S., et al. “Aerobic Exercise Intervention, Cognitive Performance, and Brain Structure: Results from the Physical Influences on Brain in Aging (PHIBRA) Study.” Frontiers in Aging Neuroscience, vol. 8, 2017, doi:10.3389/fnagi.2016.00336.
  6. Ming, Guo-Li, and Hongjun Song. “Adult neurogenesis in the mammalian brain: significant answers and significant questions.” Neuron vol. 70,4 (2011): 687-702. doi:10.1016/j.neuron.2011.05.001
  7. Mora, Francisco. “Successful brain aging: plasticity, environmental enrichment, and lifestyle.” Dialogues in clinical neuroscience vol. 15,1 (2013): 45-52.
  8. Sagi, Yaniv, et al. “Learning in the Fast Lane: New Insights into Neuroplasticity.” Neuron, vol. 73, no. 6, 2012, pp. 1195–1203., doi:10.1016/j.neuron.2012.01.025.
  9. Tomasi, D, and N D Volkow. “Aging and Functional Brain Networks.” Molecular Psychiatry, vol. 17, no. 5, 5 July 2011, pp. 549–558., doi:10.1038/mp.2011.81.
  10. Tsai, Chia-Liang, et al. “Impact of Acute Aerobic Exercise and Cardiorespiratory Fitness on Visuospatial Attention Performance and Serum BDNF Levels.” Psychoneuroendocrinology, vol. 41, 2014, pp. 121–131., doi:10.1016/j.psyneuen.2013.12.014.
  11. Andrew S. Jackson; Xuemei Sui; James R. Hebert; Timothy S. Church; Steven N. Blair. Role of Lifestyle and Aging on the Longitudinal Change in Cardiorespiratory Fitness. Arch Intern Med, 2009; 169 (19): 1781-1787