What 23andMe’s Genetic Test Won’t Tell You About Risk of Alzheimer’s Disease

By | May 31, 2017

In April 2017, 23andMe received approval from the U.S. Food and Drug Administration (FDA) to sell a genetic health risk test directly to consumers.

The resulting DNA test report contains interesting information on “wellness” traits, such as how quickly one will metabolize caffeine, predispositions to alcohol flush reaction, sleep movement, lactose intolerance, and more.

The 23andMe test also includes a handful of “Genetic Health Risks”, including testing for a risk gene associated with late-onset (after age 65) Alzheimer’s disease. While Alzheimer’s can occur at age 65 or younger, the vast majority of cases happen a decade later or more:

However, the risk of developing Alzheimer’s disease is a complex picture that can’t be told by a single gene. There are a number of other genes that influence Alzheimer’s risk, along with a person’s health history and lifestyle habits.

A Very Incomplete Story from a Single Gene Test

The 23andMe test for Alzheimer’s risk evaluates the Apolipoprotein E (APOE) gene, and determines whether the submitted DNA reads positive or negative for a specific variant of APOE – namely the E4 variant:

Carrying one or two copies of the APOE/E4 variant can increase the risk of developing late-onset Alzheimer’s disease.

However, the test leaves out other important information about the same gene, such as whether the subject also carries a copy of the APOE/E2 variant, which provides a level of protection against Alzheimer’s disease. Why 23andMe left out this important detail is a mystery.

An addition, there are several (dozens) of other genes that can affect the total genetic risk for Alzheimer’s. Still in the research lab, scientists are developing a polygenic hazard score (PHS) for Alzheimer’s that will evaluate the impact of many genes on risk of developing the disease.

The Other Part Of Alzheimer’s Risk: Environment & Choices

Your genetic profile plays only a part in Alzheimer’s risk. A number of health factors (hypertension, high cholesterol, diabetes) and lifestyle habits (food choices, exercise, sleep, etc) can have a large overall effect on either increasing or decreasing risk of Alzheimer’s.

Curious to know more? Try the Healthy Brain Test and get your summary report online.

Are Genetic Counselors the Next Pharmacists?

A final thought on consumer genetics testing. It’s not reasonable to expect everybody to start a crash course in genetics counseling to understand their own results, and the actual number of trained genetics counselors is very small.

A class of health care professionals uniformly spread throughout the country could be trained on the basics of genetics results – the pharmacist model could work here. In the meantime, caveat emptor on DNA consumer kits.