by Joshua Grill, PhD April 12, 2017
On April 6, the US Food and Drug Administration (FDA) partially reversed an earlier decision to halt direct-to-consumer (DTC) genetic testing by the company 23andMe, a personal genomics company based in Silicon Valley. The new decision approves the company to provide “genetic health risk reports” for 10 diseases, including 8 rare disorders—Alpha-1 Antitrypsin Deficiency, Celiac Disease, Early-Onset Primary Dystonia, Factor XI Deficiency, G6PD Deficiency, Gaucher Disease, Hereditary Hemochromatosis, and Hereditary Thrombophilia—and two common age-related neurological disorders—Parkinson’s disease and Alzheimer’s disease (AD).
After age, the strongest risk factor for AD is genetics. The e4 allele of apolipoprotein E (APOE) is by far the strongest identified AD risk gene. If you “carry” one or two copies of e4, however, it does not guarantee that you will develop AD. Similarly, you can still develop AD if you lack e4. Moreover, the degree to which e4 increases risk remains uncertain, with recent studies causing even more uncertainty about just how much risk is increased.
Nevertheless, studies also demonstrate that many people want to know their genetic risk for AD. The Risk Evaluation and Education for Alzheimer’s (REVEAL) study set out to examine whether people could safely be told their APOE genetic status; that is, whether learning APOE status could cause clinical depression or anxiety. The authors of this important study found that people with a family history of AD who were randomly assigned to learn their genetic status and were e4 carriers were no more likely to develop anxiety or depression than those who did not learn their status or those who learned they did not carry the e4 allele. These results have been cited time and time again as supportive of DTC genetic testing. But REVEAL used a very prescribed methodology. All participants were screened to make sure that they were not already depressed or anxious and then they underwent in-person education and counseling before genetic testing and in-person counseling to learn their results. Subsequent iterations of REVEAL, and studies in other areas of medicine, have examined whether simpler processes, like using educational brochures or telephone counseling can be used without sacrificing safety, and most find that they can. Still, no study has examined whether there are risks associated with simply allowing someone to sign up and receive their genetic results without any interaction with medical professionals. Of note, 23andMe does offer fee-for-service genetic counseling and anyone considering undergoing genetic testing in any setting should first seek genetic counseling.
Another remarkable finding from the REVEAL study is that those who learn they are at increased risk for AD are likely to engage primarily in two health behaviors: they purchase long-term care insurance and they take vitamin supplements. There is no evidence to support the latter in reducing AD risk, let alone preventing disease. Moreover, people who learn they are e4 carriers do not at greater rates begin exercising or eating a healthier diet. Yet adopting these and other protective lifestyle strategies such quitting smoking, maintaining a healthy body weight, and managing high cholesterol and blood pressure could significantly reduce the number of AD cases in the US and worldwide.
So, should you learn your AD genetic risk? The decision is now up to you. But before you do, perhaps you should consider what you would do if you found out you are at increased risk…and whether you should do those things anyway.
