Are You Predisposed to Alzheimer’s Disease? What to Consider Before Taking a Genetic Test

It is now easy and relatively inexpensive for consumers to take tests that reveal basic information about their genetic health and ancestry. The market for such tests is booming, a trend that will likely continue following the U.S. Food and Drug Administration’s recent streamlining of the approval process for bringing tests to market.

One of the more popular tests, 23andMe, costs $199 and can reveal a number of genetic predispositions. For example, you can discover if you are predisposed to lactose intolerance or a tendency to drink a lot of coffee. It can also tell you whether or not you have one of the genetic markers that increase your chance of developing Alzheimer’s disease.

The popularity of 23andMe and similar tests is understandable. If you know you have a risk for certain medical conditions, you can take steps to try and prevent them. You can avoid specific foods, take the right vitamins, exercise regularly, or visit the doctor more frequently for screening. However, what about diseases that cannot be prevented by steps like these, or diseases that have no cure, such as Alzheimer’s? Do you really want to know that you are predisposed to developing a life-threatening medical condition?

An article on HuffPost explores this question and quotes Erica Ramos, incoming president of the National Society of Genetic Counselors. She frames the question this way: “Everyone needs to think about how much they want to know. There are people who say, ‘Information is power’ and thrive from learning as much as possible. Then there are others who say, ‘You can’t prevent it. You can’t treat it. You can’t modify your lifestyle. Why would I want to know?’”

The FDA has recognized this dilemma. When it approved 23andMe it required the company to make consumers choose whether they wanted to receive reports about their predisposition to late-onset Alzheimer’s disease and Parkinson’s disease. After ordering, test takers are warned that: “If you tend to feel anxious or have ever been diagnosed with anxiety or depression, you may have more emotional difficulty with these reports.” In addition, the site, urges consumers to meet with a genetic counselor before they receive the results.

It is important to note that if you take a genetic test and the results indicate you have APOE4, the genetic variant associated with late-onset Alzheimer’s disease, you are not destined to develop Alzheimer’s. “It’s not a diagnosis,” said Ramos, “And it’s just one factor. Your chance of getting late-onset Alzheimer’s is a mix of your environment, family history and DNA. That can be a complicated message to tease out.”

Even if you have one copy of the APOE4 variant, you are still unlikely to develop Alzheimer’s. For example, a woman with a single copy of APOE4 has a five to seven percent chance of getting Alzheimer’s by the age of 75. The rate increases to between 27 and 30 percent by age 85. (However, for women with two copies of the variant the risk increases to 60 percent by age 85.)

In addition, there are a number of potential genetic variants besides APOE4 associated with late-onset Alzheimer’s that are not captured by the 23andMe test. Nor does the test screen for the rare early onset version of Alzheimer’s. Finally, some people develop Alzheimer’s without possessing any copies of APOE4 genes whatsoever.

Still, genetic counselors warn you should think long and hard about how you would react to knowing you have a predisposition for Alzheimer’s or other diseases. “What I’m hoping is that the people who can handle this information are the people who seek it out,” said Leila Jamal, a genetic counselor and bioethicist at the Berman Institute at Johns Hopkins University. “The people who can’t aren’t going to be running to pay $200 to have this done.”