Ask the Doctors

Genetic testing for Alzheimer's

Question:

Alzheimer'sruns in my family. Will it help to get gene testing for this disease?

Answer:

A relatively small fraction of cases of Alzheimer's disease begin between the ages of 30 and 60a type called early-onset Alzheimer's disease. In most people with this form of the disease, the cause is one of several mutant genes that the person has inherited from a parent. If someone inherits one of these mutated genes, it is very likely (but not certain) they will develop the disease.

Testing for these genes is costly and is not usually covered by insurance. At this time, there is no treatment proven to prevent or slow the onset of the disease. Relatively few people who have close family members with early-onset Alzheimer's choose to be tested. Others, however, insist on being tested. Some want to know if they are at risk, to help make plans for the rest of their lives. For them, living with uncertainty is worse than getting bad news. Others want to know so that they can volunteer for experimental treatments designed to slow or prevent the disease.

Most cases of Alzheimer's disease start after age 60. At this time, there is one gene identified that is a reasonably strong predictor of this more typical form of Alzheimer's disease. Everyone carries two copies of this gene, one inherited from each parent. The gene comes in four different types. People who inherit two copies of the "at risk" gene are much more likely to develop Alzheimer's compared with people who have no copies of the gene.

However, most doctors do not recommend that people get tested for this gene. That's because you want to know if you are going to get Alzheimer's disease or not, and the gene does not give you a solid answer. If you inherit two copies of the gene you may still avoid Alzheimer's, and if you inherit no copies you may still get it. Nevertheless, some people want to know if they are at increased risk.

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