Alzheimer’s Disease – What Do We Know?

Risk factors for Alzheimer’s; what we can do to prevent the disease.
In today’s population, Alzheimer’s disease (AD) is becoming more and more prevalent. This is because it is a disease associated with ageing; as we live longer, the incidence of Alzheimer’s becomes greater. It is therefore becoming increasingly important for us to learn more about the disease so that one day we can find a cure. What is Alzheimer’s and how can we reduce the risk?

What is Alzheimer’s?
Alzheimer’s is a neurodegenerative disease resulting from neuronal cell death in the brain. Alzheimer’s is characterised by a large number of amyloid plaques in the brain that surround neurones, and this can result in vascular damage. The main component of these damaging plaques is amyloid-β protein, and it is the deposition of this protein that leads to neurofibrillary tangles and cells loss. Many people know someone with this disease, however there is currently no cure and the disease kills more people than breast cancer and prostate cancer combined. There’s a variety of symptoms that you can spot in a person with Alzheimer’s. Note that it is advisable that anyone with the below symptoms should visit a doctor. A typical symptom is a gradually worsening ability to remember new information, which occurs as a result of the death of neurones which are involved in memory. Other symptoms include challenges in solving problems, problems with words, misplacing things, confusion and mood changes.

brain

Figure 1: Image showing the loss of brain mass that occurs as a result of Alzheimer’s. Note that the ventricles (spaces within the brain) are larger in the pathological condition case. Image sourced from http://aforalzheimer.blogspot.co.uk/.

What are the risk factors for Alzheimer’s?
Unfortunately there are many risk factors for this neurodegenerative disease that we cannot change. The greatest risk factor for Alzheimer’s is age; as an individual gets older, their chance of developing Alzheimer’s increases. This was found in a study on the age-specific incidence of Alzheimer’s in a community (Liesi et al., 1995). They found that the incidence of Alzheimer’s disease was 14 times high among persons older than 85 years compared with those between 65 and 69 years of age. Another risk factor is family history; the more family members a person has with Alzheimer’s, the greater their risk of developing the disease. This is because there are genes known to be involved in Alzheimer’s. A study into the genetic background of Alzheimer’s (A.Rocchi et al., 2003) identified three genes responsible for the rare early-onset (where symptoms are typically seen before the age of 60) form of the disease. These are the amyloid precursor protein (APP) gene, the presenilin 1 (PSEN1) gene and the presenilin 2 (PSEN2) gene. These are called deterministic genes, meaning that anyone who inherits them will develop the disorder. However this rare, familial form of AD accounts for only 5% of all cases. The remaining 95% are mostly late-onset cases, of which the cause is a complex one involving environmental factors as well as genetic ones. A gene called apolipoprotein E (APOE-e4) has been found to be associated with sporadic late-onset AD cases, as well as being the only gene with a confirmed role in AD. Scientists estimate that APOE-e4 may be a factor in up to 25% of Alzheimer’s cases. If a person inherits this form of APOE, they have an increased wisk of developing the disease. Genetic testing for the above genes is available, however not routinely recommended by doctors.

There are various risk factors for Alzheimer’s based on a person’s medical history. Conditions that affect the cardiovascular system, such as diabetes, high blood cholesterol and strokes are implicated in developing Alzheimer’s disease: if an older person has had a stroke, it doubles their risk of dementia. Although the link isn’t clear yet to scientists, people who have had depression later in life are significantly more likely to develop dementia. In addition, a link between Alzheimer’s and Down’s syndrome has also been observed.

What are lifestyle factors that we can change in order to reduce the risk?
Recent research is beginning to tell us more about risk factors that we could influence through lifestyle choices, and effective control of other health conditions. One known risk which we can prevent is head trauma. It has been suggested that deposits that form in the brain as a result of a head injury lead to dementia. A study which investigated this risk factor was conducted by A. Borenstein Graves et al, (1989). They explored a case study of 130 matched pairs, matched by age and sex. They found that a history of head injury resulting in loss of consciousness or that caused the subject to seek medical care was recorded in 24% of the cases and 8.5% of the controls, leading to an odds ratio of 3.5. Ischemic heart disease is implicated in vascular dementia. Your brain requires oxygen, and as each heartbeat pumps approximately 25% of your blood to your head, if this is not saturated with oxygen then the brain is also deprived. You can manage this risk by monitoring your blood pressure and cholesterol levels, and speaking to your doctor about how to reduce the risk of cardiovascular disease. Weight management is another factor important in preventing Alzheimer’s. Managing your diet can reduce the risk of high blood pressure and heart disease which, as mentioned above, increases the risk of dementia. Reducing the consumption of saturated fat is one way we can reduce the narrowing of the arteries, thus reducing the risk of developing vascular dementia.

Another dietary element that we can manage is the consumption of vitamin D; low levels are associated with an increased risk of dementia. Vitamin D can be obtained from eggs and oily fish. You should avoid cigarettes as it has an extremely harmful effect all over the body, including blood vessels in the brain. Research suggests that light to moderate amounts of alcohol may protect the brain against Alzheimer’s. However drinking above the recommended amounts of alcohol can significantly increase the risk of Alzheimer’s. In addition, ongoing research into the effect of social activity has suggested that people who are more socially active have a reduced risk of developing the disease. Puzzles that challenge the brain are considered as increasing the brain’s ability to compensate for damage that Alzheimer’s may incur, and so are encouraged to prevent disease onset. A study into the 7 main risk factors for Alzheimer’s, namely diabetes, midlife hypertension, midlife obesity, smoking, depression, cognitive inactivity or low educational attainment, and physical inactivity, found that up to half of AD cases worldwide (17·2 million) and in the USA (2·9 million) could be attributable to these factors (Barnes, D. et al., 2011). The study suggested that a 10–25% reduction in all seven risk factors could prevent as many as 1–3 million AD cases worldwide.

 

How can we help Alzheimer’s suffers?
We can help fund the amazing research that is supported by Alzheimer’s Research UK by donating to the cause via the following link: http://www.alzheimersresearchuk.org/support-us/donate/ . If you’d like to learn more about Alzheimer’s, you can click on the following link https://www.alzheimers.org.uk/ . Look out for volunteer groups in your area to help the ageing community. You can also help by educating friends and family about Alzheimer’s so that they know how to recognise the symptoms and are more aware of the causes.

References

https://www.alzheimers.org.uk/site/scripts/documents_info.php?documentID=102

http://www.alzheimersresearchuk.org/research-projects/research-early-onset-dementia/

American Psychiatric association. 1994. Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV).  4th Revised edition. American Psychiatric Press Inc.

Hebert, L., Scherr, P., Beckett, L., Albert, M., Pilgrim, D., Chown, M.,Funkenstein, H., and Evans, D. 1995. Age-Specific Incidence of Alzheimer’s Disease in a Community Population. JAMA. 273(17), pp. 1354-1359.

Rocchi, A., Pellegrini, S., Siciliano, G., Murri, L. 2003. Causative and susceptibility genes for Alzheimer’s disease: a review. Brain Research Bulletin. 61(1), pp. 1-24.

Borenstein Graves, A., White, E., Koepsell, T., Reifler, B., Van Belle, G., Larson, E., and Raskind, M. 1990. The Association Between Head Trauma and Alzheimer’s Disease. American Journal of Epidemiology. 131(3), pp. 491-501).

Barnes, D., and Yaffe, K. 2011. The Projected Risk Factor Reduction On Alzheimer’s Disease Prevalence. The Lancet Neurology. 10(9), pp. 819-828.

Author: Jess Stonehouse 

Editor: Molly Campbell 

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