Alzheimer's disease causes
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
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Overview
The cause of Alzheimer's disease is poorly understood. Research indicates that the disease is associated with plaques and tangles in the brain.[1]
Causes
It is likely that the causes include genetic, environmental, and lifestyle factors. Because people differ in their genetic make-up and lifestyle, the importance of these factors for preventing or delaying Alzheimer’s differs from person to person.
In a very few families, people develop Alzheimer’s disease in their 30s, 40s, and 50s. Many of these people have a mutation, or permanent change, in one of three genes that they inherited from a parent. We know that these gene mutations cause Alzheimer’s in these “early-onset” familial cases. Not all early-onset cases are caused by such mutations.
Most people with Alzheimer’s disease have “late-onset” Alzheimer’s, which usually develops after age 60. Many studies have linked a gene called APOE to late-onset Alzheimer’s. This gene has several forms. One of them, APOE ε4, increases a person’s risk of getting the disease. About 40 percent of all people who develop late-onset Alzheimer’s carry this gene. However, carrying the APOE ε4 form of the gene does not necessarily mean that a person will develop Alzheimer’s disease, and people carrying no APOE ε4 forms can also develop the disease.
Most experts believe that additional genes may influence the development of late-onset Alzheimer’s in some way. Scientists around the world are searching for these genes. Researchers have identified variants of the SORL1, CLU, PICALM, and CR1 genes that may play a role in risk of late-onset Alzheimer’s.