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Causes of Alzheimer's disease
No single factor has been identified as a cause for Alzheimer's disease. It is likely to be a combination of factors:
- Age is the greatest risk factor for dementia, with most cases affecting people over 65.
- It appears that there is a clear genetic link in a few families, where the disease appears relatively early in life, although developing the disease in such families is by no means inevitable. In the vast majority of cases however the effect of genetic inheritance appears to be very small.
- It is a feature of Down’s syndrome, and 15% of people with Alzheimer’s disease have a family history of Down’s syndrome. Recent research has concentrated on the gene for a substance called beta-amyloid protein that is found in the tangled fibre masses in brains of people with Alzheimer’s disease and in those of older people with Down’s syndrome. The gene for this protein is on chromosome 21. This is the same chromosome of which an extra copy is present in every body cell of people with Down’s syndrome.
- Environmental factors are being studied but nothing has been clearly identified. The concerns concerning aluminium causing Alzheimer’s disease have largely been discounted.
- It has also been suggested, but without any convincing clinical evidence, that mercury in dental amalgam might be responsible for causing Alzheimer’s disease.
- People with severe head or whiplash injuries appear to be at increased risk of developing dementia.
- Research has also shown that people who smoke and those who have high blood pressure or high cholesterol levels increase their risk of developing Alzheimer's.
