Risk Factors
Risk factors do not cause Alzheimer's Disease on their own, but they suggest an increased probabilty of developing the disease. Evidence suggests a number of factors that are thought to increase the risk of developing Alzheimer's Disease.
- Age:
The most prominant risk factor for Alzheimer's Disease is age. The risk of developing the disease is highest in over 65 year olds, with the probabilty of developing Alzheimer's Disease doubling every five years from then on. At the age of 85, the probabilty of developing the disease is 50%.
- Gender:
The probabilty of developing Alzheimer's Disease is twice as likely in women than in men. This is thought to be due to the hormone changes experienced during menopause, primarily the decrease is oestrogen.
Women have a higher life expectancy than men, and age is the major risk factor of developing Alzheimer's Diease.
Also, the probabilty of developing Type II Diabetes is higher in women - Type II Diabetes is also a risk factor for Alzheimer's Disease (see below).
- Family History:
A person is more likely to develop Alzheimer's Disease if a family member has suffered/ is suffering from the disease.
Familial Alzheimer's Disease/Early Onset Alzheimer's Disease is inherited and rare, being present in less than 10% of Alzheimer's patients. It is caused by a dominant mutation on either chromosome 1, 14 or 21. Therefore, the offspring of a mutated patient has a 50% probabilty of recieving the mutated chromosome.
Chromosome 21 contains the gene for the amyloid beta precursor protein. Down's Syndrome is caused by trisomy 21 (an extra chromosome 21), it is due to this fact that the majority of Down's Syndrome suffers develop Alzheimer's Disease by the age of 40.
Late Onset Alzheimer's Disease has no proven link to inheritence.
- Genetics:
A number of genes have been discovered that are thought to be involved in the development of Alzheimer's Disease, including APOE-4. See 'Genetics' page for more details.
- Lifestyle:
High alcohol intake, drug use, smoking and little exercise all increase the potential risk of developing Alzheimer's Disease.
A low educational background is also believed to increase the changes of developing Alzheimer's Disease, as stimulation of the brain is thought to offer protection.
- Head injuries:
A severe head injury can increase the risk of developing Alzheimer's Disease, however it does not necessary determine its onset. The frequency and severity of the head injury determines the level of risk imposed, with some head injuries never leading to the development of the disease.
- Existing medical conditions:
There is thought to be an increase in the likelyhood of developing Alzheimer's Disease if you suffer from Cardiovascular Disease, Type II Diabetes or Down's Syndrome.
Cardiovascular diseases generally include an increase in blood pressure. An increased blood pressure in the brain can cause Alzheimer's Disease.