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The Genetics of Alzheimer’s: What to Know Before Taking a Test

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Alzheimer

By Rebecca Wang, MS, CGC

November is both National Alzheimer’s Disease Awareness and National Family Caregivers Month, making this a fitting time to discuss the genetics of a disease that touches many people - directly and indirectly. Alzheimer’s disease is a progressive, neurological disease and is the most common cause of dementia in elderly adults. People who have Alzheimer’s disease suffer from profound memory loss and cognitive decline, often losing the ability to perform daily tasks on their own.  It is natural for people to worry about their risk of developing Alzheimer’s, especially if they have seen people in their lives suffer from this debilitating illness. But think twice before getting genetic testing for Alzheimer’s: it is only one small piece of the puzzle.

Before I can tell you why to proceed with caution, let me give a brief overview of Alzheimer’s genetics. In short, research on Alzheimer’s genetics has made significant progress in recent years, yet there is still a lot we do not understand about the heritability of the disease.

About 5% of Alzheimer’s disease is classified as early-onset, meaning it is diagnosed before age 60. There are three genes – APP, PSEN1, and PSEN2 – that are known to cause early-onset Alzheimer’s disease. Clinical testing for these genes is available for individuals with a relevant family history. There are also cases of early-onset Alzheimer’s where individuals do not have a genetic mutation that is thought to cause their illness.

The majority of Alzheimer’s is late-onset (diagnosed after age 60) with age as the biggest risk factor. There is one gene that has been identified as a susceptibility gene for late-onset Alzheimer’s disease: the APOE gene. Unlike the three genes associated with early-onset Alzheimer’s, APOE is a risk factor not a causative gene.

Every person has two copies of the APOE gene, but there are different variants, or forms, of this gene. One variant, known as “e4”, is a risk factor for late-onset Alzheimer’s. Studies have shown that individuals with one copy of e4 have an increased risk for Alzheimer’s disease, and individuals with two copies have an even higher risk.

Because there is no treatment or prevention for Alzheimer’s disease, there is no clinical action to take if someone has an e4 variant. APOE testing is currently not clinically recommended as a test to predict the likelihood of Alzheimer’s in people without symptoms.

Notably, direct-to-consumer genetic testing company 23andMe offers APOE variant testing to their customers. For those considering this test, it is critical to remember that APOE is a risk factor and not a disease-causing gene. This means that having theAPOE e4 variant alone is not enough to cause Alzheimer disease. It also means that people without the e4 allele still develop Alzheimer’s disease. There are many other factors, such as environment and family history, that influence whether a person will develop Alzheimer’s disease.

The American College of Medical Genetics and the National Society of Genetic Counselors both advise against direct-to-consumer APOE testing, due to its limited clinical utility and low predictive ability. While this testing can offer people an answer about one small piece of their genetics, it is ultimately not a complete picture of their health risks.

If you are concerned about inheriting Alzheimer’s, or any other disease, a genetic counselor can help you understand your risk and your testing options. Genetic counselors are also trained to help individuals anticipate the potential psychological implications of testing for a late-onset disease they have no control over, making them a crucial part of testing for incurable diseases like Alzheimer’s. To locate a genetic counselor near you, you can use the National Society of Genetic Counselor's Find a Genetic Counselor tool.


Photo credit: National Human Genome Research Institute

References

[1] Bekris LM, Yu C-E, Bird TD, Tsuang DW. Genetics of Alzheimer Disease. Journal of geriatric psychiatry and neurology. 2010;23(4):213-227. doi:10.1177/0891988710383571.

[2] Goldman JS, Hahn SE, Catania JW, et al. Genetic counseling and testing for Alzheimer disease: Joint practice guidelines of the American College of Medical Genetics and the National Society of Genetic Counselors. Genetics in Medicine. 2011;13(6):597-605. doi:10.1097/GIM.0b013e31821d69b8.

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Sharing Traditions and Family Health History at the Thanksgiving Table

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Thanksgiving

By Jason Rothstein, MPH

For many years, my family celebrated what we called Indian Thanksgiving. We made tandoori-style turkey with a basmati rice stuffing, samosas instead of mashed potatoes, curried vegetables, and loaves upon loaves of stuffed naan. We liked to think if it as Thanksgiving as it would have been celebrated had Columbus found the continent he actually intended to reach.

At the time, I lived on the far north side of Chicago, so it usually fell to me to do the Devon Avenue shopping. I could get samosas, breads, and lox for Friday morning, all in one giant trip. It was my favorite grocery shopping of the year.

One of my strongest memories of these trips was witnessing two women, who seemed to be neighbors but not close to one another, run into each other. One of them, wearing a sari, was loaded down with bags from one of the Indo-Pak bodegas. The other, a Chinese woman, carried several sacks from one of the East Asian markets, as well as a bag with a large live fish. They greeted each other warmly, and immediately started trading notes in thickly accented English about what they were making for the holiday, and about how much they were looking forward to having their families home.

In the U.S., Thanksgiving brings families together no matter what those families look like. And in the Jewish community, Thanksgiving is a chance to get together without worrying too much about how we express (or don’t express) Judaism, or about the complexities faced by many interfaith families. For this reason and others, Thanksgiving is the perfect time to talk about family health history.

My wife, Annie, is Jewish. Her sister Dara is Jewish, and married to Mike, who was raised Catholic. It’s true that they’re both usually at our Seder table in springtime, but it’s at our Thanksgiving table where we sometimes get to see his parents, his sibling, and his grandfather. It’s the only time of year when we can all exchange information, ask questions, and find commonalities in our family health histories.

We all bring our traditions to the Thanksgiving table. As Catholics from Minnesota, for Mike’s family that means dishes like Snickers salad. Go on, click the link.

But we also all bring our personal health knowledge that may help other members of the family, and we bring pieces of the puzzle when it comes to filling in the gaps left by those no longer with us. In Jewish families, this can be an acute problem, with large number of ancestors lost in Europe.

In all families, there are topics we just don’t talk about enough, or in the case of difficult subjects like cancer, may not talk about at all. If I share what I know, and my mother shares what she knows, and my uncle shares what he knows, we may just realize that a relative’s illness referred to in coded language might have been something with a hereditary component. It gives us more information to bring to our own healthcare providers when we talk with them about our family history.

Bring your health information to Thanksgiving this year. Bring a willingness to share. Bring questions you have for your family and for your in-laws. Bring a resolve to do more to understand your family health history and take action to protect yourself and the ones you love.

(But if you leave the Snickers salad at home, I for one will not mind.)

The Office of the Surgeon General offers a wealth of resources to help families talk about their health histories in November. Visit their website for information and tools.

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Affordable, Accessible Genetic Screening in Illinois

Our affordable, accessible carrier screening program uses advanced technology to provide comprehensive screening for Jewish and interfaith couples. Visit our Get Screened page to learn more and register.

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Do You Know What's In Your Genes?

What is the most valuable gift you can give to your family? The gift of good health! There are many health conditions that run in families. Knowing your family health history can alert you to the potential risk for a variety of genetic disorders . Talk to your relatives for warning signs and assess your risk for hereditary cancers.

Did you know: Ashkenazi Jews are 10 TIMES more likely to have BRCA mutations, which significantly increases lifetime risks for hereditary cancers, so what does this heightened risk mean for you? Click here to learn more .