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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 1 in 20 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 with 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 showing reduced activity (right) and normal brain (left).
What causes 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).
Which genes have been associated with Alzheimer’s disease?
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.
The location of genes that are associated with Alzheimer disease.
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