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Apolipoprotein E-4 Genetic (DNA) Test - Topic Overview

Most people who develop Alzheimer's disease do not have a history of the disease in their families. But if you do have a family history of Alzheimer's disease (one or more members of a family have had the disease), then your risk of getting it is higher. When a disease is found in families, the cause could be genetic (heredity), something in the environment, lifestyle choices, or a combination of these things.

A blood test can look for a substance that seems to increase a person's risk for Alzheimer's disease. The gene is called apolipoprotein E-4 (ApoE-4). The presence of ApoE-4 cannot predict for sure whether a person will develop Alzheimer's disease. Many people who have the ApoE-4 gene do not get Alzheimer's disease, and many people who do not have the gene still develop the disease. Most experts do not consider ApoE-4 testing a necessary or useful part of evaluating a person with suspected Alzheimer's disease.

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Sundowning

Sundowning, or sundown syndrome, affects some people who have Alzheimer's disease and dementia. People with dementia who "sundown" get confused and agitated as the sun goes down -- and sometimes through the night. Sundowning may prevent people with dementia from sleeping well. It may also make them more likely to wander. Due to the stress it puts on caregivers, sundowning is a common cause of caregiver burnout.

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Early-onset Alzheimer's

Sometimes people develop Alzheimer's disease at a young age, between the ages of 30 and 60. This is referred to as early-onset Alzheimer's disease or autosomal dominant Alzheimer's disease. It is not common (less than 5 out of 100 cases), and this form of the disease has been linked to defects in specific genes. There is a 50% risk that these genes will be passed on. A person who inherits the genetic defect will most likely develop Alzheimer's disease.

    This information is produced and provided by the National Cancer Institute (NCI). The information in this topic may have changed since it was written. For the most current information, contact the National Cancer Institute via the Internet web site at http:// cancer .gov or call 1-800-4-CANCER.

    WebMD Medical Reference from Healthwise

    Last Updated: October 29, 2012
    This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.
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