Exercise as it relates to Disease/Exercise and its effects on preventing Alzheimer's disease

This is a critique of the research article 'Effects of Aerobic Exercise on Mild Cognitive Impairment' by Laura D. Baker, PhD, et al. (2010) from the JAMA Neurology Journal.

This critique was written as an assignment in Health, Disease and Exercise at the University of Canberra.

Background to Research

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There is a great deal of research on the topic of Alzheimer’s Disease (AD) and the effects of exercise as an intervention to slow down cognitive degeneration in Elderly populations. With no distinct cause known for the disease, the need for research on the topic proves paramount. One leading theory to prevent the effects of the disease is the intervention of regular moderate to high intensity exercise.

AD is a progressive neurodegenerative disease that impairs memory and cognitive judgement, most commonly in the elderly. Due to its impacts on cognitive function, it is the leading cause of Dementia and is associated with increased morbidity and mortality.

The causes of AD are yet to be proven however, it is thought to be due to a number of different factors. AD is characterised by inexorable loss of neurons, particularly in the hippocampus and cerebral cortex as well as the formation of senile plaques and neurofibrillary tangles on brain cells. Theories of the cause of AD are mostly associated with; acceleration of aging, degeneration of anatomical pathways, environmental factors…, genetic factors including mutations… a metabolic disorder resulting in mitochondrial dysfunction, vascular factors and infecting agents.

Senile Plaques, a common biomarker of AD, are formed from extracellular deposition of beta-amyloid peptides in the brain. From various studies on mice, exercise has shown to reduce amyloid deposition in the cerebral cortex thus slowing down the effects of AD on an individual. Other benefits of exercise contributing to neuroprotection include alleviating memory loss in elderly, reducing inflammation and apoptosis markers. With these benefits proved on mice in controlled trials, it then would be feasible to think they could be replicated in humans.

This study also sparks as an area of interest as the intervention of exercise is an inexpensive and unintrusive method of slowing down the effects of AD. With the total spending on Health in 2019-20 for Australia coming to $81.8 billion, 16.3 per cent of total Australian Government expenditure, this intervention could save money as well as individual’s lives.

Where is the research from?

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This research is from the JAMA Neurology Journal Vol. 67, No. 1 (2010). JAMA is an internationally peer-reviewed general medical journal with the key objective of promoting the science and art of medicine and the betterment of public health.

This particular article was concerned with the effects of aerobic exercise on cognition and other biomarkers associated with AD for older adults and sex as a predictor of response.

What kind of research was this?

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This research was a six month, randomised and controlled clinical trial on 33 adults. 17 being female and 13 males that had amnestic mild cognitive impairment.

What did this research involve?

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The research involved randomly dividing the participants into high-intensity aerobic exercise or a stretching control group. The aerobic group were prescribed exercise for 4 days/week at 75-85% Heart Rate Reserve (HRR) for 40-60 min/day, for 6 months. The controlled group carried out stretching activities to the same schedule but were required to keep their heart rate(HR) at or below 50% of HRR. Before and after the study, glucometabolic and treadmill tests were performed, and fat distribution was assessed using DXA scans. Blood was also collected at baseline, 3 months and 6 months. Cognitive tests were also administered. The Performance measures collected include:

• β-amyloids 40 and 42.
• Symbol-Digit Modalities
• Verbal Fluency
• Stroop
• Trails B
• Task Switching
• Story Recall
• List Learning
• Fasting plasma levels of insulin
• Cortisol
• Brain-derived neurotrophic factor
• Insulin like growth factor-I

Results

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The basic results saw that high-intensity aerobic exercise had sex-specific effects on cognition, glucose metabolism and hypothalamic-pituitary-adrenal axis and trophic activity.

For Females, aerobic exercise improved performance on multiple tests of executive function, increased glucose disposal during metabolic clamp and reduced fasting plasma levels of insulin, cortisol and brain derived neurotrophic factor.

In Males, Aerobic exercise increased plasma levels of insulinlike growth factor 1 and had a increased performance only on trials B performance. These results also saw an increase in cardiorespiratory fitness and a loss of body fat in both sexes.

Beta Amyloid levels were recorded to decrease in Aerobic exercisers and increase in the stretching group however, the differences recorded failed to reach statistical difference.

These results have been replicated in other similar trials proving validity in that a specific improvement on executive function and brain activation changes can be attributable to exercise.

Conclusions

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Conclusions we can take from this research is that Aerobic Exercise can be used as a potentially inexpensive non-pharmaceutical intervention to slow the effects of AD and lower biomarkers associated with the disease. More research will be needed to replicate and fill gaps in the research such as the impact of exercise on Beta Amyloid peptides.

The results also suggest that a sex bias in cognitive response may relate to sex-based differences in glucometabolic and hypothalamic-pituitary-adrenal axis responses to aerobic exercise; as was present in the female results.

Practical advice

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From the results of this study, coupled with the growing thought that exercise may help to prevent and/or help to slow the effects of AD, it can be thought that regular Aerobic Exercise can prove somewhat effective.

Regular Aerobic Exercise proved to considerably drop particular biomarkers of AD in the participants of the trial, particularly females. Therefore, proving exercise should be undertaken by the elderly, especially females, to mitigate against AD.

Weekly exercise of 30 minutes of moderate intensity physical activity on most, if not all days of the week are encouraged by the Australian Government. Examples of exercise that could be prescribed to meet these guidelines and replicate the study’s findings include; Water aerobics, Power walking and Hiking. Not only will these exercises mitigate against AD but increase cardiorespiratory fitness and reduce body fat.

However, if an individual is not able to meet these levels of exercise they should start with 10 minutes once or twice a day. After two weeks, make it 15 minutes twice a day then they will have reached the goal of 30 minutes per day.

Further information/resources

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Further sources for information on exercise guidelines for the Elderly and exercise’s effects on AD can be found below:

• Physical Activity Recommendations for Older Australians – AUS Gov.: https://www1.health.gov.au/internet/publications/publishing.nsf/Content/phd-physical-choose-health-l~phd-physical-choose-health-l-recommendations
• Alzheimer’s Disease – Dementia Australia: https://www.dementia.org.au/about-dementia/types-of-dementia/alzheimers-disease
• Preventing Alzheimer’s Disease – Helpguide.org: https://www.helpguide.org/articles/alzheimers-dementia-aging/preventing-alzheimers-disease.htm#:~:text=According%20to%20the%20Alzheimer's%20Research,started%20to%20develop%20cognitive%20problems.