Genetics and Health

Testing for Alzheimer’s Genes

by Hsien Hsien Lei, PhD on July 10th, 2005

A few months ago, 454 Life Sciences announced they would be sequencing the entire genome of James Watson, co-discoverer of the structure of DNA. The only thing he didn’t want to know was his apolipoprotein E (APOE) genotype. (Personal Genome, May 25, 2005).

ApoE4 is one form of the APOE gene that has been associated with increased risk of Alzheimer’s. A recent study examined the psychological and behavioral effects of telling people their APOE genotype and found no real difference between those who knew and those who didn’t. (Science Daily, June 25, 2005)

Aside from ApoE4, other risk factors for Alzheimer’s disease are age, family history, and gender. Most people with Alzheimer’s don’t develop the disease until after age 65. For every five years after 65, the risk of developing Alzheimer’s doubles, and after age 85, the risk is almost 50 percent. Previous data have shown that people with a parent or sibling with Alzheimer’s have a two- to three-fold increase in risk. (Alzheimer’s Association)

Study participants were divided into two groups; both groups were assessed for risk of Alzheimer’s based on the usual risk factors, but only one group was told their APOE genotype. Instead of a higher level of anxiety and depression in the group that was given information on their APOE genotype, researchers found no significant difference in negative feelings between the two groups.

In fact, participants who were told their APOE genotype would actually choose to be assessed again and many would even recommend it to family and friends. Carriers of ApoE4 at higher risk of developing Alzheimer’s were also more likely to make changes to their insurance plans.

While these results are interesting, I don’t have enough information to know whether they would be applicable to the general population. We don’t know the average age of the study participants. They may be elderly and have come to terms with a less active life. Or they may be young enough to be optimistic that even if they’re carriers, medical science will come up with something to save them. And of the group who knew their genotype, the number who tested positive for ApoE4 could have been very small so the majority would have been free of anxiety and depression because they were not ApoE4 carriers.

I might be interested in getting tested when I’m nearing 65 and if I have relatives who are also affected. There isn’t any way to prevent or cure Alzheimer’s disease at this time, but there are some treatments that can slow the disease’s progression. That probably wouldn’t be my primary concern, though. I’d get tested so that I have some lead time on the disease to make sure that my family and friends all knew how I much I loved and cared for them. I’d make the necessary arrangements for my own care and the care of others who depend on me. Even without the threat of disease, those are things I should be doing anyway.

Would you want to be tested for ApoE4? What would you do if you were positive?

“As new treatments are developed to delay the onset of Alzheimer’s, it is going to be critical to identify those at greatest risk,” says Robert C. Green, a medical doctor and professor of neurology at Boston University School of Medicine. “At the same time, it will be very important that genetic risk assessment is done carefully and communicated accurately so individuals feel empowered by the results and are able to maintain a positive outlook and a good quality of life.”

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POSTED IN: Genetic Testing