Environmental factors also significantly influence the development of Alzheimer’s Disease. Although genetic makeup can have a definitive effect in early-onset Alzheimer’s, its influences are more variable in the late-onset form. Many studies have been carried out to establish the extent of environmental influences on the development of Alzheimer’s. Due to the fact these factors are largely modifiable, they have attracted a great deal of interest.
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  Diet and exercise are thought to have critical importance in the development of Alzheimer’s. To discuss the science that explains this, we can look at the theory of oxidative stress.
  Oxygen free-radicals are very reactive forms of oxygen which are produced as a by-product of respiration. The free radicals react with other molecules inside the cell to oxidise them. Antioxidants are substances which stop this oxidation. Oxidative stress occurs when more oxygen free-radicals are produced than are counteracted by protective antioxidants. It is thought to be particularly prevalent in the brain, where a great deal of respiration occurs. The current theory suggests that oxidative stress contributes to cognitive decline in normal ageing, but this effect is increased in Alzheimer’s disease.

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 In this way diet has a direct impact on the ageing process. Theoretically, a diet high in antioxidants should decrease the prevalence of oxidative stress and thus decrease the risk of Alzheimer’s Disease. An experiment in 2005 investigated this. Aged beagles were fed an antioxidant-enriched diet over a period of three years and their cognitive functions were tested. Beagles were selected as test subjects because of their cognitive functions can be assessed in similar ways to humans. The results showed improvements in memory and learning. In addition, the amyloid plaques became visibly reduced during the three year period, suggesting that the antioxidants actually helped to destroy the deposits.

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 Regular exercise is also believed to lower the risk of developing Alzheimer’s. In 2012, experiments were carried out into the effects of exercise. Researchers controlled the level of exercise in two groups of mice. The mice were then placed in a water maze* as a test of learning and memory skills. The mice that had experienced a higher level of exercise performed better on these tests. Brain scans also showed that high levels of exercise increased levels of brain derived neurotrophic factor (BDNF). This is a protein which is produced in normal brain function, but its levels are significantly lower in Alzheimer’s patients. 

While it seems that diet and exercise may play some part in memory loss, no studies have been done on this topic with humans. And as we'll see later, there are LOTS of environmental factors which may affect Alzheimer's. But even if it's not been proven, it's always good to look after your body. As they say; 'healthy body, healthy mind'.

*To see an example of a Morris water maze, watch this youtube video: http://www.youtube.com/watch?v=LrCzSIbvSN4 
   
References

Alzheimer’s Association, 2012. Inside the Brain: An interactive tour [online] Available at: <https://www.alz.org/braintour/alzheimers_changes.asp> [Accessed 18 July 2012]

HBO : Documentaries : The Alzheimer’s Project, 2012. [online video] Available at: <http://www.hbo.com/alzheimers/supplementary-the-connection-between-insulin-and-alzheimers.html> [Accessed 12 July 2012]

Lane, N., 2002. Oxygen: The Molecule that made the World. Great Britain: Oxford University Press
 


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