If you have just learned you are ε4/ε4

What it means

You inherited the ε4 form of the APOE gene from both parents. About 2–3% of people do¹. It is the strongest common genetic risk factor for late-onset Alzheimer’s disease.

In a large 2024 study, nearly all ε4/ε4 carriers had Alzheimer’s changes in the brain by older age, and symptoms began on average around age 65, earlier than in people with other genotypes². The authors proposed that ε4/ε4 be treated as a genetic form of Alzheimer’s.

What it does not mean

• It is not a diagnosis. Brain changes can be present for years before any symptoms, and not everyone develops dementia. One study estimated lifetime risk by age 85 at about 51% for ε4/ε4 men and 60% for women, versus 11–14% overall³.
• Risk differs between people. It varies with age, sex and ancestry⁴, and rare protective variants can offset ε4⁵.
• Your relatives’ risk is not the same as yours. Each of your children inherits one of your two ε4 copies, so each is at least an ε4 carrier; what they inherit from their other parent also matters.

Practical next steps

• Talk to a genetic counselor. They can explain your result, what it means for family members, and whether further testing makes sense. Search the National Society of Genetic Counselors directory.
• Tell your doctors before any anti-amyloid treatment. ε4/ε4 carries the highest risk of brain swelling and bleeding (ARIA) with lecanemab and donanemab. US labels advise APOE testing before treatment⁶, and in the EU these drugs are not approved for ε4 homozygotes. See Drugs.
• Work on the risk factors you can change. The 2024 Lancet Commission estimated that nearly half of dementia cases are linked to 14 modifiable factors, including high blood pressure, hearing loss, high LDL cholesterol, physical inactivity, smoking, diabetes and social isolation⁷. These estimates are for the general population; how much they shift risk specifically in ε4/ε4 is less certain.
• Consider research. Some trials enroll only ε4 carriers. See Trials, or the Alzheimer’s Association’s free TrialMatch service. GeneMatch, run by Banner Alzheimer’s Institute, matches adults aged 55–75 without dementia to studies by APOE genotype using a cheek swab; it does not tell you your result.
• Know your legal protections. In the US, the Genetic Information Nondiscrimination Act protects you in health insurance and employment, but not for life or long-term care insurance⁸. Consider this before sharing your result.
• Find others. ApoE4.Info is a long-running nonprofit community of ε4 carriers.