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What Causes Alzheimer's Disease?
Scientists do not yet fully understand what causes Alzheimer's Disease. There
probably is not one single cause, but several factors that affect each person
differently. Age is the most important known risk factor for Alzheimer's
Disease. The number of people with the disease doubles every 5 years beyond age
65.
Risk Factors involved with the cause of Alzheimer's Disease
Family history is another risk factor. Scientists believe that genetics may
play a role in many Alzheimer's Disease cases. For example, early-onset familial
Alzheimer's Disease, a rare form of Alzheimer's Disease that usually occurs
between the ages of 30 and 60, is inherited. The more common form of Alzheimer's
Disease is known as late-onset. It occurs later in life, and no obvious
inheritance pattern is seen in most families. However, several risk factor genes
may interact with each other and with non-genetic factors to cause the disease.
The only risk factor gene identified so far for late-onset Alzheimer's Disease
is a gene that makes one form of a protein called apolipoprotein E (ApoE).
Everyone has ApoE, which helps carry cholesterol in the blood. Only about 15
percent of people have the form that increases the risk of Alzheimer's Disease.
It is likely that other genes also may increase the risk of Alzheimer's Disease
or protect against Alzheimer's Disease, but they remain to be discovered.
Other areas of study concerning the cause of Alzheimer's Disease
Scientists still need to learn a lot more about what causes Alzheimer's
Disease. In addition to genetics and ApoE, they are studying education, diet,
and environment to learn what role they might play in the development of this
disease. Scientists are finding increasing evidence that some of the risk
factors for heart disease and stroke, such as high blood pressure, high
cholesterol, and low levels of the vitamin folate, may also increase the risk of
Alzheimer's Disease. Evidence for physical, mental, and social activities as
protective factors against Alzheimer's Disease is also increasing.
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