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Scientists lay the case for a genetic cause for Alzheimer’s
Insights from The New York Times, Kaiser HealthNews, The Washington Post
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A new study published this week in Nature Medicine suggests that perhaps a fifth of all Alzheimer’s disease cases could have a genetic cause. The findings could lead to a new understanding of the disease and how it is passed down in families, as well as opening the door to a diagnostic test and new treatments.
Right now, there is no cure for Alzheimer’s and treatment options are confined to supportive therapies designed to help people live with the disease.
The researchers looked at data from 500 people with two copies of the gene APOE4 and found almost all of them developed clear symptoms of Alzheimer’s by age 55. By 65, they had extremely high levels of amyloid proteins — a hallmark of Alzheimer’s that build up and create plaque in the brain — as well as signs of cognitive decline.
APOE4 has been linked to Alzheimer’s before, but this study takes that further, arguing it isn’t a risk but a cause. Experts say that if accepted as a genetic form of Alzheimer’s, this new disease classification would broaden the scope for treatment and prevention — it would also be one of the most common genetic diseases in the world.
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Transforming our understanding of Alzheimer’s disease
The causes of Alzheimer’s, which affects some six million Americans, are both obscure and multi-faceted. However the new study’s authors say their evidence shows in some cases, it “can be tracked back to a cause, and the cause is in the genes.” Classifying APOE4 as a genetic form of Alzheimer’s could also help identify more cases with a genetic cause earlier and lead to more personalized treatments targeting this form of the disease, specifically. “We may need to start treating these as a separate group in our research papers,” said one study author.
Current tests for Alzheimer’s don’t allow for early diagnosis
An Alzheimer’s diagnosis typically requires extensive mental, physical, and neurological exams, as well as brain imaging to determine whether someone has the disease. Early indicator tests are few, far between, and generally not very accurate. In 2023, for example, medical testing company Quest Diagnostics released a blood test targeted at people 50 and older called AD-Detect that measures elevated levels of amyloid-beta proteins, but the rate of false-positives is worryingly high, as Kaiser HealthNews reported. Tests for the APOE4 gene also exist right now but there is a shortage of genetic counselors and supportive services to help patients navigate their results. “It totally backfired,” one expert told Reuters who had hoped early testing would provide reassurance.
Alzheimer’s treatment is limited at best, unavailable at worst
Alzheimer’s has no cure, but there are some drugs that might slow its effects in some people. In 2023, the US Food and Drug Administration approved Leqembi, an intravenous infusion drug shown to slow Alzheimer’s in some cases. But for people with two-copies of the APOE4 gene, drugs like Leqembi can cause “serious and life-threatening events,” including brain swelling and bleeding. Leqembi is also $26,500 per year, or $5,000 per year with Medicare coverage, and is administered at specific infusion centers that are not accessible to many. “How will patients get the drug if they don’t typically go to big medical centers? That includes rural patients and African Americans and Latinos, who typically receive less Alzheimer’s care than their White counterparts,” The Washington Post reported.
