May 09, 2024
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A new study indicates that having two copies of a specific gene variant should be designated as a cause of Alzheimer's disease, not just a risk factor. The Alzheimer's Association recommends people receive genetic counseling and obtain all necessary information before they consider genetic testing.
A new study suggests that certain genes are not just a risk factor for Alzheimer's disease but actually cause at least one type of the condition. Yet, people shouldn't rush to get genetic testing, according to the recommendations from the Alzheimer's Association.
The study, published in the journal Nature, indicates that people with two copies of a specific gene variant are almost certain to get Alzheimer's, and that they might be diagnosed through genetic testing before symptoms develop.
Previous research has shown that people who inherit two copies of the APOE4 variant are at a dramatically higher risk of developing Alzheimer's. But the new study concluded that the APOE4 homozygosity – having two copies of the genetic variant – should actually be classified as a cause of the disease. About 50% of Alzheimer's patients have one copy of the APOE4 variant compared to 15-20% of the population with two copies.
However, the "Alzheimer's Association cautions against routine genetic testing of healthy individuals for risk of Alzheimers or other dementia until an individual has received genetic counseling and understands the information necessary to make an informed decision, including the social and economic factors that could be impacted by having this genetic information," Kristina Fransel, executive director of the nonprofit's Delaware Valley Chapter, wrote in an email.
"At this time, genetic tests that determine susceptibility or risk for Alzheimer's or other dementia are primarily of value in a research setting or for clinical trials."
In the study, researchers found that nearly everyone in a group of more than 500 people with two copies of APOE4 showed biological markers of Alzheimer's by 55. By 65, nearly all of the participants had "abnormal amyloid levels in cerebrospinal fluid," an indicator of Alzheimer's.
Limitations of the study included a lack of diversity among the participants.
The findings of the study "need to be replicated and confirmed, in particular in study populations that more accurately reflect the diversity of people living with Alzheimer's disease," Fransel said. "If this idea is correct, it may have implications for the way Alzheimer's risk is assessed; the way Alzheimer's research studies are conducted; how some types of Alzheimer's treatments are developed.
"If you do choose to get genetic testing — for any reason — you should receive genetic counseling before a test is ordered and when the results are obtained," Fransel added. "A genetic counselor can help make an informed decision about testing and can interpret the results and help navigate next steps.
"Importantly, if a person is genuinely concerned about their dementia risk, or the risk of a loved one, based on family history or symptoms, they should consider adopting healthier lifestyle habits, regardless of their genetic status."
