APOE Gene Test: General Information on APOE4, Alzheimer's Risk and Genetic Counseling

The APOE gene gives instructions for a protein involved in moving cholesterol and fats through the body, and some of its variants have been linked to Alzheimer's and heart disease risk. This article explains what an APOE test is, what it can and cannot tell you and who might consider genetic counseling, as general information. A test result does not predict disease; always review results with your doctor or a genetic counselor.

What is the APOE Gene?

The APOE gene is involved in giving your cells instructions on how to make a protein (apolipoprotein E) that helps move cholesterol and other types of fat through your body. It does this by merging the protein with fats (lipids) to form lipoproteins. The APOE gene has three types, also known as alleles. These are:

• APOE-ε2 (APOE2).
• APOE-ε3 (APOE3).
• APOE-ε4 (APOE4).

Each person inherits a copy of the APOE gene from each of their biological parents. Certain health conditions can be affected by the specific combination of the APOE gene types and how your body moves cholesterol and other fats through your blood.

Which APOE Gene Causes Alzheimer's Disease?

Unfortunately, there has not been any specific gene identified that shows to directly cause Alzheimer's disease. However, studies have shown that your risk of developing diseases like dementia and Alzheimer's may increase if you have at least one copy of the APOE4 gene.

Alzheimer's disease has two types that are based on the age at which it starts: Late-onset and early-onset. Those who develop Alzheimer's after the age of 65 are considered late-onset, while those who develop it before age 65 are early-onset. The disease slowly causes memory loss (dementia).

Though the APOE4 gene might increase the risk of developing Alzheimer's, those who have at least one APOE2 gene may have a lower risk. If the disease does occur in a person with this type, it often occurs later in life than those with the APOE4 gene.

Risk Factors for Alzheimer's Disease

Age is one of the most common risk factors for Alzheimer's and other types of dementia, even though these diseases are not a normal and natural part of aging. Their risk is typically a combination of factors. Family history is also included in these risk factors. Research suggests that those who have direct family members with Alzheimer's are more likely to develop the disease. Your lifetime risk can increase if you have more than one family member with the condition. Lifestyle and environmental factors, like poor sleep, smoking, cardiovascular disease, or diabetes, can also increase your risk.

Test results of genetic counseling show that genes are involved in increasing the risk of Alzheimer's disease. There are two categories of genes that influence whether you might develop this disease. These are:

• Risk Genes: These are the types we mentioned earlier - the APOE genes that can increase your risk of developing a disease but do not guarantee that you'll get it.
• Deterministic Genes: These are the genes that ensure and directly cause you to develop a condition. According to scientists, less than 1% of cases of Alzheimer's are caused by these deterministic genes.

What is APOE Genetic Testing?

APOE genetic testing helps to identify which type of apolipoprotein E (APOE) genotype you have. By identifying this, you'll better understand what type of risk you might have for developing Alzheimer's disease since having a specific genotype (like APOE4) can increase your risk.

A higher risk of developing a condition does not mean you'll develop it. This information only tells you whether or not you might be more likely to. There are many things that go into your risk of developing certain conditions - genetics being one of them. So, just because you might have the gene that is connected to an increased risk of Alzheimer's does not mean you'll end up developing it. It's important to discuss test results with a genetic counselor.

The Link Between APOE Gene and Diseases

Understanding your health can start with discovering how your APOE gene is linked to various diseases. Specifically, as we mentioned, this gene shows whether you have a higher chance of getting diseases like Alzheimer's and even heart disease. Depending on the type of APOE gene, you might have a higher chance of getting specific diseases.

That's what makes this genetic testing so valuable. It can help you understand the link between your genetics and disease risk so that you can discuss it with your doctor or a genetic counselor.

The Connection Between APOE and Alzheimer's Disease

Scientists have focused a lot of research on the APOE gene and how it is linked to Alzheimer's disease. This condition is serious as people slowly lose their memory and sense of self. In researching the APOE gene, they've found that the APOE4 version can put someone at a higher likelihood of getting Alzheimer's after the age of 65. Having one copy of this specific gene seems to double or triple a person's genetic risk for Alzheimer's.

However, just because the risk might be there does not mean a person will develop it. In fact, lifestyle factors, family history, and other factors like ethnicity can contribute to a higher risk of causing this disease than having this specific APOE gene.

There are also ways to decrease your risk. Research suggests that regular physical activity is associated with better overall brain health and a lower likelihood of cognitive decline; talk to your doctor about what suits you.

Who Should Get Tested for APOE Genetic Variants?

Testing for the APOE genetic variants isn't always recommended because there can be many causes for the development of diseases, and it is unlikely to be caused by a single gene. In other words, the results of this genetic test can't fully predict whether a person will develop Alzheimer's disease.

However, testing for early onset of the disease might be helpful if you have a family history of Alzheimer's disease. If you're someone who has a direct relative, like a parent or sibling, who has been diagnosed with early-onset Alzheimer's, you might want to consider genetic testing, especially if that relative is no longer around to be able to test. Talking through the results with a doctor or genetic counselor can help you plan next steps.

What Knowing Your APOE Status Can Mean

If you have a direct relative with Alzheimer's disease, you might want to discuss genetic counseling with your doctor before deciding on a test. Here are some of the benefits that could help you figure out whether or not to test:

Early Intervention

Knowing early on whether you could be at a higher risk can help you have a more informed conversation with your doctor about healthy lifestyle choices. This might mean making lifestyle changes such as eating better, getting more physical activity, lowering stress, and stopping or reducing smoking or drinking.

Personalized Treatment

When you know your APOE status, you can discuss it with your doctor or a genetic counselor. For example, if there's a chance you could have a higher risk for heart problems in the future, your doctor may talk with you about things like cholesterol and blood pressure checks.

Healthcare Planning

Being able to understand your APOE status can make your healthcare planning easier. Once you know, you can talk with your doctor or a genetic counselor about your possible risks for illnesses, what signs you should be on the lookout for, and what choices you can start making to stay healthy.

The APOE gene test is intended to provide you with information regarding your risk for certain conditions like Alzheimer's disease and heart disease. Though your APOE status might not be specifically related to whether or not you develop these diseases, it can give you information about whether you could be at a higher risk - especially if you have a strong family history of these conditions.