Scientists have yet to fully understand the role genes play in a person’s risk for, or development of, Alzheimer’s disease. Research suggests that having a family history of the disease can elevate risk. However, a person can still develop Alzheimer’s if they don’t have relatives with the disease.
The most well-known and well-studied gene associated with Alzheimer’s risk is called the APOE gene.
There are three common forms, called alleles, of this gene: APOE ε2, APOE ε3, and APOE ε4. Only the ε4 variety heightens Alzheimer’s risk, but does not cause the disease.
Every person inherits two APOE alleles: one from their mother and one from their father. About 25% of the population has one copy of the APOE ε4 allele, while only 2-3% have two copies. Having the two copies substantially increases disease risk.
Genetic testing can determine which APOE alleles a person has. Some researchers use genetic testing to learn more about causes of Alzheimer’s disease, and to help identify at-risk individuals and develop treatments. Testing can also shed light on how genes may interact with lifestyle and environmental factors to increase risk.
The Brain Health Registry GenePool Study
This past February, BHR researchers published a new paper on findings from the Brain Health Registry GenePool Study. This study aimed to identify older Brain Health Registry participants at risk for Alzheimer’s based on genetic testing and online cognitive, health, and lifestyle data.
Aa total of 573 older BHR participants participated in this study by contributing DNA samples via saliva test kits mail to their homes. The researchers used a custom online portal to monitor the saliva samples and communicate with participants.
A Stanford University laboratory analyzed the DNA and found that about a quarter of participants had at least one APOE ε4 allele. Having two copies of the APOE ε4 allele was associated with worse scores on online cognitive tests, compared to having only one ε4 allele or no ε4 alleles. These results were consistent with previous findings that APOE e4 may affect memory and thinking, and showed that online cognitive tests are able to detect these effects.
Participants also completed a survey of their experiences and attitudes toward participating in the study. Positive participant experiences, alongside successful remote saliva collection methods, suggest that researchers could employ these same methods to efficiently conduct future genetic research studies using a remote approach.
Although unknowns remain, researchers are continuing to learn more about the relationship between genetics and Alzheimer’s disease, as well as risk genes besides APOE.
It is very unlikely that genetic testing will ever predict a person’s likelihood of developing the disease with 100% accuracy. This is because there are also environmental factors that can influence disease onset and progression. However, genetic testing, used with other disease screening methods, is still an important tool for researchers.