Saturday, 14 May 2016

Alzheimer's Disease

Before tackling this notorious disease, the difference between dementia and Alzheimer's must be clarified. Dementia is a symptom caused by Alzheimer's disease, and is characterised by memory loss as well as many other cognitive processes.  

Alzheimer's itself is a progressive disease that affects 520,000 people in the UK. Its causes are unknown, although there are a number of factors that increase the risks of developing this disease. These include: if it is in the family history, experiencing a severe head injury and increasing age. As a result, the condition  is most common  in sufferers aged 65, with women also at greater risk. Research has also shown that the lifestyle factors associated with cardiovascular disease, such as smoking and obesity, also correlate with Alzheimer's disease.

Mainly the cognitive abilities are affected gradually with Alzheimer's. The first signs are usually minor memory loss, but this can then progress to problems with communication, hallucinations, confusion and personality changes.

All of Alzheimer's symptoms characterise the symptoms of dementia, which can be explained by understanding the changes the disease causes in the brain. In essence, the condition stimulates nerve cell death, which can deteriorate large portions of brain tissue.

Diagram showing the middle part of a healthy and diseased brain
As a result, many areas of the brain are lost. The cerebral cortex shrivels, removing with it the billions of cells, called grey matter, which control thinking and processing.  In addition, the hippocampus also experiences shrinkage, which thus affects the storage of long term memory and the ability to recall specific events. Also, the ventricles, which are cerebrospinal fluid-filled sacs, increases in size. This creates a build up of pressure as the brain is forced to press against the skull. 
Areas of loss in AD brain compared to healthy brain
Under a microscope, scientists are able to identify the extent that the disease affects the brain. At high magnification, the brains of sufferers show fewer nerve cells and synapses, which are fundamental for the travel of neurones and thus the travel of information in the brain. Nerve cells are also affected. Abnormal pieces of the amyloid precursor protein (APP) form aggregated plaques by clumping together, blocking these synapses and again preventing the transport of information. 
In healthy brain tissue, proteins named tau provide orderly tracks, allowing the transport of nutrients and other essential materials to cells. However, the disease causes these tau proteins to twist and from tangles. The once orderly tracks therefore disintegrate, stopping the delivery of materials, causing the cells to die.

Acetylcholinesterase inhibitors are most commonly used to treat Alzheimer's. Like in their name, these drugs are used to inhibit the enzyme that breaks down the neurotransmitter acetylcholine, therefore allowing the acetylcholine to remain for longer and increase the activity of cholinergic neurones. The inhibitors prescribed for the early to middle stages of Alzheimer's include donepezil, galantamine and rivastigmine.

Alzheimer's - A progressive disease

Notoriously, sufferers with Alzheimer's deteriorate over time as the disease develops and conquers more of the brain. The time this takes differs from person to person, but it is largely affected by how early the sufferer was diagnosed and any other diseases they may have. Therefore, although on average, sufferers survive for 8 years, some may live for 20 years.

The early stages of the disease is also referred to as early dementia or mild cognitive impairment. Often at this stage, memory loss is not drastic, with short term memory mostly affected and adversely, long term largely retained. The ability to think or plan, known as executive functioning, may also be difficult. This is all due to the tangles beginning to form in areas of the brain that control these cognitive abilities.


These symptoms develop and worsen over time, leading to middle stages of Alzheimer's disease, also known as the moderate stage. Some sufferers here will show more aggressive behaviour, such as refusing to take orders. Again this frustration is as a result of the more drastic damage to synapses and nerve cells, making performing tasks and making decisions difficult. Unable to remember certain events, confusion and mood changes are also other characteristics of this stage of dementia.

At the final stages of the disease, sufferers become almost completely dependent on their carers. Physically, sufferers at this stage may lose many essential functions of movement, including swallowing and walking. Not only do they become mentally vulnerable, but their immunity weakens causing sufferers to become prone to infections such as pneumonia. As their cognitive abilities deteriorate, holding a conversation becomes near to impossible and all the severity of all symptoms before heighten. 


Stages of Alzheimer's disease and its effects on the brain
References:
Alzheimer's society(2016)Alzheimers.org.ukRetrieved 14 May, 2016, from https://www.alzheimers.org.uk/site/scripts/documents_info.php?documentID=100

NHS UK. (2016)www.nhs.ukRetrieved 14 May, 2016, from http://www.nhs.uk/conditions/Alzheimers-disease/Pages/Introduction.aspx

Alzorg(2016)AlzorgRetrieved 14 May, 2016, from http://www.alz.org/alzheimers_disease_what_is_alzheimers.asp

NHS uk(2017)www.nhs.ukRetrieved 16 February, 2017, from http://www.nhs.uk/Conditions/Alzheimers-disease/Pages/Treatment.aspx