Family history
Most Alzheimer's disease is not passed down directly from parent to child. It develops from a combination of age, genes, heart and blood-vessel health, and other factors, and you can influence many of them.
Having a parent, brother, or sister with Alzheimer's does raise your risk, and the risk is higher when more than one close relative has the disease. Family history raises the odds, and many people with an affected parent never develop Alzheimer's themselves.
The APOE gene
The gene researchers study most is called APOE. Everyone inherits two copies, one from each parent. One version, APOE4 (sometimes written APOE ε4), is the strongest known genetic risk factor for Alzheimer's that begins after age 65. About one in four people carry one copy of APOE4, and roughly 2 to 3 percent carry two copies.
Carrying one copy raises risk, and carrying two copies raises it further. Even so, APOE4 is a risk gene. Many people who carry it never develop Alzheimer's, and many people who develop Alzheimer's have no copy at all. An APOE result tells you about odds, and it cannot tell you whether or when you will get the disease.
Genes that cause early-onset Alzheimer's
A small number of families carry a change in one of three genes, APP, PSEN1, or PSEN2, that causes Alzheimer's directly. These inherited forms account for less than 1 percent of all cases. Symptoms usually begin before age 65, often in a person's 40s or 50s, and each child of a parent who carries the change has a 50 percent chance of inheriting it.
The pattern to watch for is several relatives, across more than one generation, who developed Alzheimer's at a young age. If that describes your family, ask your doctor for a referral to a genetic counselor.
Genetic testing
Medical guidelines do not recommend routine APOE testing for people without symptoms, because the result cannot predict your future and does not change the steps that protect your brain. Some people still want to know. That is a personal decision, and the best way to make it is with a genetic counselor, who can explain what each possible result would mean before you test and help you and your family afterward.
Consumer DNA kits can report APOE status. If you use one, you may learn your result with no one there to explain it, and the result can also reveal information about your parents, brothers, and sisters.
APOE testing does matter in one situation: before starting Leqembi or Kisunla. People with two copies of APOE4 have a higher risk of a side effect called ARIA (swelling or small bleeds in the brain that show up on MRI), so your care team uses the result to weigh risks and benefits and to plan monitoring.
Insurance protections
A federal law, the Genetic Information Nondiscrimination Act (GINA), protects you from genetic discrimination by health insurers and by employers with 15 or more employees. GINA does not cover life, disability, or long-term care insurance.
Florida goes further than federal law. A 2020 Florida law bars health, life, and long-term care insurers from canceling, limiting, or denying coverage, or setting different premium rates, based on genetic test results. Insurers can still consider a diagnosis that is already in your medical record. If you are shopping for long-term care insurance, talk with an advisor about timing before any testing.
Next steps
- Tell your primary care doctor about your family history, including the age at which each relative's symptoms began.
- If you or your family are noticing memory changes, schedule a memory evaluation. Even without symptoms, a baseline evaluation gives your doctors a reference point for the future.
- Work on the risk factors you can change: blood pressure, blood sugar, cholesterol, hearing, physical activity, sleep, smoking, and social connection. Our guide to lowering your risk covers each one.
- Ask about research. Prevention studies enroll people with a family history who have no symptoms, and the Alzheimer's Association's free TrialMatch service can help you find one.
- If several relatives developed Alzheimer's before age 65, ask for genetic counseling.
Worry about Alzheimer's after watching a parent go through it is common, and it is a good reason to take your brain health seriously. If memory changes have already started, early evaluation matters most, because today's treatments work in the early stages of the disease.
This guide is for education and is not medical advice. Treatment decisions are made with your provider after a full evaluation.