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What is Alzheimer’s disease?
Alzheimer’s disease is the most common cause of dementia – a condition which leads to the impairment of some mental abilities and communication skills. It affects one in twenty people over 65, and more than 1 in 10 of those over 85. Alzheimer’s disease is caused by the gradual death of certain brain cells, especially in the areas involved in memory, judgement and reasoning. The impairments associated Alzheimer’s disease can eventually be devastating: people often don't recognise their families, and forget where they live or how to take care of themselves.
PET scan of an Alzheimer disease brain (right) and normal brain (left).
What happens in Alzheimer’s disease?
The first signs of Alzheimer’s disease are memory loss and changes in behaviour and personality. Doctors look for a decline in mental abilities by testing the patient's memory and attention span. Brain scans can detect changes in the brain as Alzheimer’s disease progresses. The mass of neurons gradually shrinks in the brains of people with Alzheimer’s disease.
People with Alzheimer's disease have difficulties with drawing a clock face with the hands at a quarter to two. This has been used as a screening test to detect AD.
Is Alzheimer’s disease inherited?
Medical research has identified five genes that influence the development of Alzheimer’s disease. Three of these genes affect younger people (under the age of 65), and two affect older people (over the age of 65). It must be remembered that Alzheimer’s disease is not a hereditary condition and by identifying the genetic ‘risk factors’ for developing Alzheimer’s disease scientists can begin to look for affective treatments.
Do we understand Alzheimer’s disease?
A type of protein called ‘amyloid’ forms ‘plaques’ which accumulate in and around brain cells causing them to die. A different type of protein called ‘tau’ forms ‘tangles’ which change the structure of brain cells. We also know that certain chemicals in the brain which transmit messages between neurons are depleted. Scientists do not yet know why the altered amyloid builds up in the brains of some people but not in others.
Tangles (below) and plaques (above).
Can we treat Alzheimer’s disease?
Modern drug treatments for Alzheimer’s disease can temporarily slow down the loss of memory in some patients. Some of the neurons that die in Alzheimer’s disease normally make a neurotransmitter called acetylcholine. Drugs that maintain the amount of acetylcholine in synapses can improve short-term memory and concentration. However, these drugs only treat the symptoms of Alzheimer’s disease and not the actual loss of brain cells. Researchers are trying to find ways to halt and even reverse this destruction.
Scientists are developing drugs that stop the build up of tangles in the brains of Alzheimer patients.
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