APOE

Updated September 17, 2019

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The APOE Gene

Many people have heard of or been impacted by Alzheimer’s disease — a brain disorder that attacks a person’s memory and cognitive skills, and worsens over time with no known cure.

But a lot of people don’t know the link between Alzheimer’s and the APOE gene.

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Disclaimer: Before You Read

It is important to know that your genes are not your destiny. There are various environmental and genetic factors working together to shape you. No matter your genetic makeup, maintain ideal blood pressure and glucose levels, avoid harmful alcohol intake, exercise regularly, get regular sleep. And for goodness sake, don't smoke.

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Also known as the apolipoprotein E gene, this genetic code is known to increase a person’s risk of developing Alzheimer’s in their lifetime.

Here’s what you should know about the APOE gene and how it is related to Alzheimer’s disease.

What Does the APOE Gene Do?

Alzheimer’s research began more than 100 years ago, with the disease named after it’s discovering physician, Dr. Alois Alzheimer.

In the decades since, researchers have still been unable to crack the code on just what causes Alzheimer’s — including the early-onset and late-onset forms of the disease — and why some people develop it and others don’t.

But when it comes to understanding a person’s risk, researchers have discovered that some types of the apolipoprotein E (APOE) gene play a role in how likely it is that someone will develop late-onset Alzheimer’s disease.

How does the APOE gene impact the chances of developing Alzheimer’s disease?

First, it’s important to understand what the APOE gene’s purpose is. The APOE gene’s main task within the body is to create a protein called apolipoprotein E.

This protein bonds with fat to create lipoproteins, which help move cholesterol through the bloodstream.

Researchers understand that there are three main kinds of APOE genes:

  • APOE e2 — the least common type of APOE, which may actually reduce a person’s risk of developing Alzheimer’s disease
  • APOE e3 — the most common type of APOE gene, which seems to have no impact on Alzheimer’s development; most people have the APOE3 gene
  • APOE e4 — a moderately common form of the APOE gene, which is known to increase a person’s risk of having Alzheimer’s

So while Alzheimer’s research notes that having an APOE e4 gene increases a person’s risk of having the disease, it’s not clear why or how it plays a role.

But observation of autopsied brains from people who had the disease shows that people who had the APOE e4 type often had more severe brain damage than those who had Alzheimer’s but didn’t have APOE e4.

APOE Gene Inheritance Pattern

The kind of APOE genes you have all comes down to inheritance. You get one APOE gene from each parent, giving you two APOE genes total.

You should know that it’s common to have two different types of APOE genes or even two of the same.

When examining APOE gene sequences, researchers have discovered two things: Having one copy of the ε4 variant increases a person’s risk for Alzheimer’s. But, having duplicates — or rather, two of the ε4 variant in the APOE gene — can drastically raise those odds.

Is APOE4 dominant or recessive, and can that impact whether you get it from your parents? Researchers believe that APOE genes — including APOE2, APOE4, and the APOE3 gene — are all dominant genes.

This means that only one parent has to have that kind of gene to pass it on to their child, as opposed to a recessive gene, which both parents must have to pass along.

Still, growing research suggests that who in your family has Alzheimer’s can impact the odds that you also have it.

Many people search for “Alzheimer’s hereditary mother or father,” trying to find out which parent gives them a higher risk.

More and more evidence suggests that having a mother with the disease increases a child’s chances, compared to having a father with Alzheimer’s.

Health Conditions Related to the APOE Gene

Many people who see family members struggle with Alzheimer’s wonder: Is Alzheimer’s genetic? Researchers understand that genetics does play a large role in whether or not someone will have the disease, but it’s not the only factor.

And, it’s important to know that having the APOE gene isn’t just linked to Alzheimer’s. APOE genes play a role in other kinds of health conditions:

  • Hearing loss: Research notes a link between the APOE gene and age-related hearing loss.
  • Dementia: People with the APOE e4 gene may be at a higher risk of developing dementia as they age, specifically a form called “dementia with Lewy bodies.” This form of the disease includes hallucinations, mood changes, impaired balance, and Parkinson's disease-like tremors.
  • Macular degeneration: People with some kinds of APOE variants may be at risk for macular degeneration, a condition that affects part of the retina and leads to distorted or lost vision.
  • Heart conditions: Researchers have determined links between the APOE gene and heart disease, as well as other heart health conditions such as atherosclerosis, skin lesions, and increased risk of heart attack and stroke. People with two APOE2 genes may be at risk for developing a condition called hyperlipoproteinemia type III. For people with two copies of APOE2, cholesterol levels may be higher and this build-up can lead to health issues and atherosclerosis.

You should know that having an APOE variant doesn’t make you more or less susceptible to developing early-onset Alzheimer’s disease.

At this time, researchers understand there may be early-onset Alzheimer’s genes, but APOE is more heavily linked to late-onset Alzheimer’s development.

Testing for APOE

According to the National Institute on Aging, just having the APOE gene doesn’t mean that a person is guaranteed to develop Alzheimer’s.

That’s because some people with APOE never develop the disease, and other people who don’t have the APOE gene are diagnosed with Alzheimer’s.

For that reason, many genetic experts and doctors don’t recommend getting using an APOE genotyping kit or having an APOE4 gene test to determine your risk of developing late-onset Alzheimer’s.

Still, some people can benefit from knowing what kind of APOE gene they carry.

Who is at risk and should get tested?

So, if having the APOE gene doesn’t guarantee that you’ll develop Alzheimer’s, but it can increase your risk, is it worth getting tested?

Because researchers don’t understand all the reasons why Alzheimer’s develops, it’s reasonable to say that everyone is at risk for developing the disease, though some people more than others.

For some people, choosing to undergo genetic testing to learn if they carry the APOE gene can give them more information and tools to plan for the future of their health. You may want to consider APOE genetic testing if:

  • You have a family history of Alzheimer’s
  • You have several other environmental and health risk factors for developing Alzheimer’s
  • You are interested in participating in Alzheimer’s research

APOE Gene Testing Options

Where can I get genetic testing for Alzheimer’s?

There are two main ways you can go about learning your APOE gene status — at-home genetic testing and clinical genetic testing.

At-home genetic testing

Many genetic testing companies have received FDA approval for their Alzheimer’s genetic testing kits.

For example, APOE gene 23andMe kits are available; these kits provided by the popular genetic testing company are often much cheaper than the cost of clinical testing.

APOE testing online results are usually available within 6 to 8 weeks, and the results are provided with a detailed report that you can share with your doctor or genetic counselor.

Clinical genetic testing

In some cases, your doctor may believe that knowing your APOE status could be a benefit.

In these cases, they may draw blood and send it to a genetic testing lab, or have you visit a hospital or outpatient clinic to have the test performed.

Test results are usually available within several days to two weeks depending on how busy the laboratory is.

APOE gene test cost

How much you pay for an APOE gene test comes down to where you obtain your test and if you have insurance coverage.

If you choose to use an at-home genetic test, you can expect to pay between $35 and $200 depending on what testing company you choose, available sales, and any additional test features you purchase.

If you want a clinical genetic test, and your doctor confirms with your insurance provider that it is necessary, it’s possible to pay nothing out of pocket.

Still, some people order clinical APOE testing through a doctor without insurance coverage. In this case, the cost can range up to several hundred dollars or more.

The Effects of Knowing Your Status

Knowing your APOE genetic status can be scary. That’s because having a certain type of APOE gene isn’t a guarantee that you will or won’t develop Alzheimer’s disease.

Many physicians recommend against having a genetic test specifically for APOE because the results can cause a lot of stress and emotional upset.

On the other hand, learning that you don’t have any APOE e4 variants may give you a false sense of security that you won’t have Alzheimer’s at some time in your life.

That’s because almost anyone can have the disease — even people with APOE e2 and e3 variants.

If you choose to have an APOE genetic test performed, the information can be a helpful tool in creating a wellness plan that benefits your health, reduces controllable risk factors (such as quitting smoking and exercising regularly), and makes plans for any future care you may have if you do end up developing the disease.

Consideration of Other Risk Factors

Researchers aren’t quite sure how APOE plays an exact role in the development of Alzheimer’s disease.

But, decades of scientific work surrounding Alzheimer’s show other factors can increase a person’s chances of developing the degenerative brain disease.

According to the Mayo Clinic, there are a variety of factors that increase a person’s risk of having Alzheimer’s, including:

  • Having a family history of Alzheimer’s, especially for close family members such as parents or siblings
  • Getting older — some research shows that the highest risk age group is people over 85, though people between the ages of 65 and 84 also have an increased risk
  • Past head injuries
  • Getting less sleep — including having a hard time falling asleep and then staying asleep
  • Health conditions such as high blood pressure, high cholesterol, and uncontrolled diabetes
  • Smoking or regular exposure to secondhand smoke
  • Obesity and a lack of exercise
  • A lack of stimulating brain activities and social engagements — studies show that people with lower levels of education who do not participate in mentally stimulating activities have a higher risk of developing the disease

Having one or two of these factors doesn’t mean that a person will definitively develop Alzheimer’s disease.

But, many of these factors combined with the APOE e4 gene could drastically increase a person’s chances of having the disease later in life.

Pros and Cons of Testing for APOE

If you’re deciding whether or not you should have a blood test for Alzheimer’s genes, specifically the APOE-E4 gene, here are some pros and cons to think about:

Pros to APOE testing

  1. Having APOE test results can help you create a plan to reduce your risk factors of getting Alzheimer’s disease
  2. You may be able to participate in clinical trials or research that could benefit others

Cons to APOE testing

  1. You may worry or feel depressed about knowing your APOE status
  2. You may quell fears that you’ll get Alzheimer’s, though the test results are not a guarantee, leading to a false sense of security

Having APOE testing done is a very personal decision that only you can make. But, working with your doctor or a genetic counselor can help you weigh the decision.

The Importance of Genetic Counseling After Testing for APOE

Choosing to work with a genetic counselor can alleviate a lot of the stress and worry associated with APOE test results. Many people who learn they have APOE 4 genes find that they are scared, depressed, and unsure of what to do next.

Having an experienced, professional genetic counselor can help take the fear out of your APOE testing results and make sense of what happens next, or how you should proceed with the results you have.

This is especially important because, at this point in research and genetic testing, the jury is still out on just how much a role APOE variants play in the development of Alzheimer’s disease.

Treatment Options

Unfortunately, there is no treatment for Alzheimer’s disease. Until recently, there has been no way to change the type of APOE genes that a person has, though newer research and emerging practices by gene therapy doctors can possibly replace mutated or unwanted genes.

Gene therapy is still new, and many of the side effects are unknown; for this reason, research is mostly targeted towards incurable diseases.

Some researchers and nutritionists believe that following an APOE gene diet can make a difference in reducing the risk of Alzheimer’s.

Many of these programs promote diets that are low in cholesterol to prevent build up and lower blood pressure — two conditions that could work with APOE e4 to trigger Alzheimer’s onset.

Following an APOE4 lifestyle change often includes reducing sugar, meat, and processed foods, exercising frequently, and kicking smoking habits.

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