Controlling Alzheimer's Risk 

elderly couple

One study shows that physical activity and diet health exert some control over Alzheimer's risk. Scientists have found possible mechanisms between physical activity and Alzheimer's risk.

Alzheimer's disease is a brain disease that causes loss of memory and cognitive function. The disease is caused by the build up of toxins in the brain leading to deterioration of brain tissue. The hippocampus, our brain's memory center, deteriorates as the disease progresses. The National Institute of Health estimates that 5.1 million Americans suffer from Alzheimer's.

In 2009 a study found negative correlations between the risk of developing Alzheimer's disease and physical activity and diet health (Physical Activity, Diet, and Risk of Alzheimer Disease, 2009, Nikolaos Scarmeas, et al.). The study looked at 1880 elderly individuals from New York City over an average period of 5.4 years. Individuals diet score and physical activity score was collected.  The study participants were screened to ensure that they were not suffering from dementia before participating in the study. Those reporting significant physical activity had a 37-50% lower risk of developing Alzheimer's disease. Those in the highest Mediterranean-style diet adherence tertile had a 32-40% reduced risk of developing Alzheimer's disease.  

Good physical activity and a healthy diet were both found to independently reduce risk of developing Alzheimer's disease. The Godin leisure time questionnaire was administered to determine physical activity. The questionnaire looked at physical activity over a two-week interval. Diet was determine with the 61-item version of the Willett Semiquantitative Food Frequency Questionnaire to determine adherence to a mediterean-type diet (points for fruits, vegetables, fish, grains and lost for meats, dairy, fats). Subsequent questionnaires were administered  every 1.5 years to ensure the validity of the initial questionnaire.

Alzheimer Disease (AD) Incidence by High or Low Physical Activity Levels and Mediterranean-Type Diet Adherence Scores                 

The participants were all 77+/-1 years old; as is the case with elderly populations  physically activity was not prevalent in the study participants.  Therefore, the high physical activity corresponded to 1.3 hours of vigorous physical activity, 2.4 hours of moderate physical activity or 4 hours of light physical activity. This demonstrates that even a small amount of physical activity can lead to significant benefits in reducing Alzheimer's.

How does exercise protect the brain?

The mechanism that exercise influences Alzheimer's Disease risk may be through various toxins and neuro-factors. Research has shown that brain-derived neurotrophic factor (BDNF) protects against synapse deterioration and may be able to treat Alzheimer’s. Moderate to vigorous physical activity increases BDNF. Low levels of Nerve Growth Factor (NGF) has been shown to be a risk factor for Alzheimer's. Like BDNF, exercise increases the brain's NGF.  Reactive oxygen species in the brain may be another risk factor for Alzheimer's.  Exercise takes care of reactive oxygen species via two pathways: exercise reduces their production and exercise raises antioxidant levels, which detoxify reactive oxygen species. Exercise has been shown in mice models to reduce expression of several genes that have been found to correlate with Alzheimer risk.

Another mechanism exercise may influence Alzheimer's risk is through cerebral blood flow and metabolism. Both cerebral blood flow and metabolism decrease with the onset of Alzheimer's. Exercise significantly increases both. Exercise increases vascular endothelial growth factor (VEGF) in the brain. VEGF spurs the development of nigral microvessels, countering the decrease in nigral micro vessel density, an effect of aging. Exercise, especially high intensity exercise, at a young age has been shown to have a tremendous impact on the the promotion of VEGF.

For more information about the biological mechanisms behind exercises reduction in Alzheimer's risk read Exercise Plays a Preventive Role Against Alzheimer's Disease (Z. Radak, et al., 2010).

In summary, physical activity and diet exert significant influence on Alzheimer's Disease risk. Although the mechanism is not exactly known, researchers speculate that it may be through neuro-factors, toxins, cerebral blood flow and cerebral metabolism, all of which are controlled by some extend through exercise. Please share your thoughts!

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