What are risk factors?
Many diseases have specific causes; for example, a virus causes measles. However, for many chronic disorders (long-lasting conditions such as Alzheimer's disease), the causes remain uncertain. In their search for answers, scientists look for factors that appear to be linked to the development of a disease. These are "risk factors" -- if they are present, there is an increased chance, but not a certainty, that the disease will develop.
Risk factors are characteristics or exposures that appear to have some relationship to the development of a disease. They can include family background, work history, or exposures to a substance or product. Some risk factors can be modified (for example, lowering blood pressure reduces the risk of stroke); other risk factors cannot be modified (for example, age or family history).
It is important to note that risk factors are not necessarily causes of a disease. No single study can verify a link between a disease and a specific factor; repeated studies are necessary before a causal link can be established.
What are the risk factors associated with Alzheimer's disease?
Age
The Canadian Study of Health and Aging; Risk Factors for Alzheimer Disease in Canada provides evidence to support age as a risk factor. The older you become, the higher the risk for Alzheimer's disease.
1 in 11 Canadians over age 65 is affected by Alzheimer's disease.
Family history
Many studies indicate that people with a relative (parent, brother or sister) with Alzheimer's disease have a greater chance of developing the disease than those with no family history.
The more common form of Alzheimer's disease is called Sporadic Alzheimer's Disease and accounts for 90 to 95 per cent of all cases. The role of heredity in Sporadic Alzheimer's Disease is unclear and continues to be the subject of intense research.
A rare form of the disease, Familial Autosomal Dominant Alzheimer's Disease (FAD), accounts for approximately 5 to 10 per cent of all cases and is known to be inherited -- the disease will occur if the disease gene is present. (Each chromosome carries many genes that are strung together like beads on a string. These genes are the basic units that allow specific characteristics to be passed from one generation to the next.)
In certain families, FAD is passed directly from one generation to another through a dominant inheritance pattern. This means that if a parent is affected, each child has a 50 per cent chance of inheriting the disease gene and developing Alzheimer's disease in adulthood.
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The information offered in this section is taken from the Alzheimer Society of Canada website. Visit their site to learn more about: