Genetics can influence a person’s risk of developing Alzheimer’s disease. The most important common genetic risk factor is APOE4, which can be identified through a blood or saliva test. Having one copy increases risk; having two copies increases it considerably more. But APOE4 is not a diagnosis—many people who carry it never develop Alzheimer’s.
Knowing your APOE status may help you better understand your risk and take greater action on potentially modifiable factors such as exercise, metabolic and cardiovascular health, diet, sleep, and other lifestyle choices. Genetic testing can also have psychological and family implications, so some people may prefer to discuss testing with a physician or genetic counselor.
The most important message is simple:
Genetic risk is not destiny.
Everyone inherits two copies of the APOE (apolipoprotein E) gene—one from each biological parent. APOE helps the body transport cholesterol and other fats and also plays important roles in the brain.
There are three common forms:
APOE2 — relatively uncommon and generally associated with a lower risk of Alzheimer’s.
APOE3 — the most common form and generally considered neutral for Alzheimer’s risk.
APOE4 — associated with an increased risk of late-onset Alzheimer’s disease.
People can therefore have combinations such as APOE2/3, APOE3/3, APOE3/4 or APOE4/4. Having one APOE4 copy increases risk, while inheriting two copies increases risk substantially more.
APOE4 is a risk factor, not a cause or diagnosis. Some people with APOE4 remain cognitively healthy throughout life, while many people who develop Alzheimer’s do not carry APOE4.
APOE4 can substantially increase the likelihood of developing Alzheimer’s disease, but it cannot predict with certainty what will happen to an individual.
Compared with people who have the common APOE3/3 combination:
One copy of APOE4 is generally associated with about a 2–3 times greater risk of developing Alzheimer’s.
Two copies of APOE4 (APOE4/4) are associated with a much higher risk, often estimated at roughly 8–12 times greater than for people with APOE3/3.
APOE4 is also associated with developing Alzheimer’s at an earlier average age. Recent research has drawn particular attention to people with two APOE4 copies because Alzheimer's-related biological changes occur in a high proportion of these individuals as they age.
These numbers should be interpreted cautiously. APOE4 does not determine your future. Risk differs according to ancestry, sex, age, other genes, cardiovascular and metabolic health, and lifestyle and environmental factors. Some APOE4 carriers live into old age without developing dementia.
This is one reason genetic testing is potentially useful but also potentially unsettling: it provides information about risk, not a prediction of whether or when an individual will develop Alzheimer’s.
A simple blood or saliva test can determine your APOE status. But whether a healthy person should be tested is still debated.
Mainstream medical organizations generally do not recommend routine APOE testing solely to predict Alzheimer’s disease in people without symptoms. The test cannot tell you whether you will develop Alzheimer’s, and learning that you carry APOE4 can cause unnecessary worry.
There are also reasons someone may choose to know. APOE status can provide a clearer picture of genetic risk and may encourage greater attention to exercise, blood pressure, metabolic health, diet, sleep, and other potentially modifiable risk factors. It may also be useful for participation in research studies.
APOE testing has become increasingly important for people considering newer anti-amyloid Alzheimer’s drugs. APOE4 carriers—particularly people with two copies—have a higher risk of ARIA, a potentially serious side effect involving brain swelling or bleeding.
For someone without symptoms who wants testing primarily for prevention, it is worth discussing the advantages and disadvantages with a knowledgeable physician or genetic counselor before deciding.
You cannot change your genes, but you can address many factors associated with cognitive decline. Having APOE4 may be an additional reason to focus on brain, metabolic, and cardiovascular health.
Important steps include regular aerobic and strength exercise, maintaining healthy blood pressure, blood glucose and insulin sensitivity, getting adequate sleep, avoiding smoking, staying socially and mentally active, addressing hearing loss, and eating a nutrient-rich diet.
Researchers are studying whether APOE4 carriers may benefit from more individualized approaches to diet, cholesterol management, omega-3s, and other interventions. Some physicians, including Dr. Dale Bredesen, use APOE status as part of a personalized prevention strategy.
Karin Dee is the founder of Brain Health Science, where she focuses on understanding the APOE4 gene and ways people with APOE4 may be able to reduce their risk of Alzheimer’s disease. She translates research on genetics, nutrition, metabolic health, exercise, sleep, cardiovascular health, and other lifestyle factors into practical information. Her central message is that while APOE4 increases Alzheimer’s risk, it does not make Alzheimer’s inevitable, and there are potentially modifiable factors that may help protect long-term brain health.
A practical introduction for people who have recently learned that they carry APOE4. Dee recommends starting with basic laboratory testing, looking more closely at genetics, improving diet, exercise and sleep, addressing metabolic and cardiovascular health, eating omega-3-rich fish, and considering selected supplements. She emphasizes making changes gradually and tailoring them to an individual’s biomarkers and risk factors.
Karin Dee summarizes the strategies she considers most important for reducing Alzheimer’s risk, especially for APOE4 carriers. They include improving metabolic health, exercise, sleep, DHA-rich fish, mild ketosis, and selected supplements. She emphasizes addressing multiple risk factors, while recognizing that you can’t do everything at once and changes can be made gradually.
Karin Dee explores emerging evidence linking adequate vitamin C levels with brain health and lower Alzheimer’s-related mortality. She explains why the brain maintains unusually high concentrations of vitamin C and why this may be especially relevant for APOE4 carriers. Her message is not to megadose, but to avoid deficiency and get the fundamentals right.
APOE status can be determined with a blood or saliva test ordered by a physician or genetic counselor. Some direct-to-consumer genetic testing services also provide information about APOE variants.
Because APOE results have implications not only for you but also for biological relatives, genetic counseling can be helpful in understanding what the results mean—and what they do not mean.
For people considering testing specifically because of Alzheimer’s risk, a test ordered through a healthcare professional may provide the clearest path to appropriate interpretation and follow-up.
APOE4 is a risk gene, but a few rare genetic mutations—primarily in APP, PSEN1, and PSEN2—can directly cause familial Alzheimer’s disease. These mutations usually lead to early-onset Alzheimer’s, often before age 65, and tend to run strongly through generations of a family.
They account for only a small fraction of all Alzheimer’s cases. Testing for these mutations is generally considered when there is an unusually early onset or a strong family history of early-onset Alzheimer’s.
A short, focused explanation of APOE4 risk and strategies Bredesen believes may mitigate that risk.
Dr. Norwitz, who carries two copies of APOE4, discusses his substantially increased genetic risk for Alzheimer’s and the diet, exercise, metabolic health, and other lifestyle strategies he uses in an effort to reduce that risk.