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Find Out if You're at Risk for Alzheimer's Like Chris Hemsworth, Who is "Taking a Break" After Tests

Neurosurgeons explain everything to know about genetic testing and who it's recommended for.  
FACT CHECKED BY Emilia Paluszek

Chris Hemsworth is taking a health warning seriously. While shooting his new docuseries, National Geographic's Limitless with Chris Hemsworth, the Thor star did genetic testing and had a frightening discovery–he's at great risk for developing Alzheimer's disease. The Disney + show follows Hemsworth and how he pushes the limits physically to naturally fight back aging. In the fifth episode "Memory," he's told he has two copies of the gene APOE4, which is linked to an increased risk of the disease. 

Hemsworth told Vanity Fair, "They took all my bloodwork and did a bunch of tests and the plan was to on-camera tell me all the results and then talk about how you can improve this and that." But plans changed once his results came in. Hemsowrth shared, "Peter Attia, who is the longevity doctor in that episode, and overseeing a lot of the show, called [show creator] Darren [Aronofsky] and said, 'I don't want to tell him this on camera. We need to have an off-side conversation and see if he even wants this to be in the show.' It was pretty shocking because he called me up and he told me."

Hemsworth's grandfather had Alzheiner's and the 39-year-old explained to Vanity Fair how he dealt with the initial shock. "Yeah, there was an intensity to navigating it. Most of us, we like to avoid speaking about death in the hope that we'll somehow avoid it. We all have this belief that we'll figure it out. Then to all of a sudden be told some big indicators are actually pointing to this as the route which is going to happen, the reality of it sinks in. Your own mortality."

Dr. Parham Yashar, MD FACS FAANS Board Certified Neurosurgeon, Stroke Medical Director Dignity Health Northridge Hospital has not treated Hemsworth but emphasizes, "What's most important to understand is that risk factors are exactly that–they are factors that can increase your risk of developing a medical condition, but they are not the causes of that medical condition. That's why if you can understand what those risk factors are, especially if they're ones that you can modify, you can still actively change your potential risk for developing a medical condition."

Eat This, Not That! Health spoke with experts that have never treated Hemsworth who explained what to know about genetic testing and who should consider undergoing the procedure. As always, please consult your physician for medical advice. Read on—and to ensure your health and the health of others, don't miss these Sure Signs You've Already Had COVID.


How Genetic Testing Works

Female laboratory assistant analyzing a blood sample at hospital.

Dr. Yashar explains, "Genetic testing is a type of blood test where the blueprints that make up your entire body (your genetic make-up, which is your DNA) are analyzed.  Blood tests are done searching for either changes (or mutations) in your DNA or just components (DNA sequences) that can be associated with various conditions or diseases. If you think of your DNA all together as a 10,000-page document, genetic testing is like using CTRL-F to find certain typos or strings of characters/words in your DNA. Your DNA can be analyzed to look for certain mutations that have been associated with medical conditions, including Alzhmeirs, cancers, and other diseases. Depending on the condition, generally genetic testing is not recommended in patients who don't have risk factors for these conditions (such as a parent, sibling, or relative with the condition)." 

Dr. Ali Mesiwala Medical Director of Neurosurgery at Dignity Health St Bernardine tells us, "Every cell in our body contains DNA. DNA is the abbreviation for deoxyribonucleic acid, the complex molecule that makes up our chromosomes and provides the instructions for the development, growth, functioning, and reproduction of every living organism and many viruses. DNA is made up of two twisted chains (a double helix) of four chemicals. These four chemicals are called nucleotide bases: adenine (A), thiamine (T), guanine (G), and cytosine (C). The human genome is made up of more than 6 billion pairs of these nucleotide bases arranged in specific sequences to make nearly 25,000 genes. Nearly 99% of all these genes are the same in each person, while the 1% that are variable make every individual unique.

Genetic testing involves the sequencing of the DNA in each individual, and then comparing this sequence of genes with a database in order to determine what genes are present, and what specific traits, risk factors, and predispositions a person may have. In order to perform a genetic test, a person swabs the inside of their mouth or spits into a vial and sends this sample to a lab. The lab then uses sterile techniques to  process the sample to separate the cells from the swab or saliva, and then through a variety of chemical processes, removes the DNA from the cells. The DNA is sequenced using a sophisticated machine to determine the genes that are present. By comparing these results to a database of other human DNA sequences, we can find out what genes are present."


The Risk of Genetic Testing

patient speaking with doctor

According to Dr. Mesiwala, "Genetic testing is a rapidly evolving field and holds the potential to provide life-changing information for everyone. The key is to understand what information and results are provided, and to make thoughtful and mindful changes based on that information. The risk is that this information can be used in a way that is harmful, and may lead to poor decision making when information is taken out of context, or results are interpreted in an inappropriate or wrong way. It is critical that patients who undergo genetic testing review the results with a trusted medical provider, and take time to understand the impact of this information on their daily lives, and in terms of their family and loved ones."

The Mayo Clinic says, "Generally genetic tests have little physical risk. Blood and cheek swab tests have almost no risk. However, prenatal testing such as amniocentesis or chorionic villus sampling has a small risk of pregnancy loss (miscarriage). Genetic testing can have emotional, social and financial risks as well. Discuss all risks and benefits of genetic testing with your doctor, a medical geneticist or a genetic counselor before you have a genetic test."


The Value and Affordability of Genetic Testing

happy family on couch

Dr. Mesiwala says, "The value of genetic testing is that it can provide you with information about your predisposition to develop certain diseases, detect diseases before they manifest any symptoms or signs, and help people decide whether to have children if they possess genes that can be passed on and cause major birth defects or childhood diseases. A positive result can allow a person to modify their lifestyle, take steps to prevent or minimize certain diseases, direct them toward treatment options, and establish ways to monitor or detect early signs of life changing diseases. It can also provide information about a person's ancestry, physical traits, and preferences. Genetic testing has become more affordable and accessible to everyone. Many commercial services are available and charge anywhere from $100-$300 to analyze your DNA. As time passes, more information is being discovered, and the results from your sample are refined. That means that the sample that you provide today may continue to yield genetic information for you for many years to come, as the genetic databases are refined, and discoveries are made."

Megan Mescher-Cox, DO Board certified in Internal Medicine, Lifestyle Medicine & Obesity Medicine with Dignity Health St. John's Hospital adds, "Genetic tests are done by blood work or sometimes by saliva.  Someone can get testing done especially if they are at higher risk for certain conditions or if they want to be tested to know their risk profile for certain diseases. New testing is coming out daily and it is becoming more affordable.  Testing is often not covered by insurance, although there is great variability with this."  


The Accuracy of Genetic Testing

Family talking over dinner.

Dr. Mesiwala says, "The accuracy of genetic testing is not about whether a gene is present or not, but rather whether having a certain gene determines or predisposes that person to have certain diseases or traits.  For example, the presence of certain genes will indicate that a person has blue eyes, black hair, or can taste certain things. Certain diseases, such as Huntington's disease, are associated with very specific genes. If a person has that gene, then they will develop that disease. These genes are called deterministic. Other genes, like APOE-4, the gene that Chris Hemsworth was found to have 2 copies of, may be found in  patients who have certain diseases, like Alzheimer's disease.  It doesn't mean that the APOE-4 gene causes Alzheimers, but having that gene is more common in people who have the disease. 

If you have the gene, there is no guarantee that you will develop Alzheimers. It means that when some patients who have Alzheimer's disease have had their DNA analyzed, the presence of the APOE-4 gene is more common in these populations. There's not a 100% relationship between having that gene or multiple copies of that gene and developing that disease. In other words, the presence of this gene may mean that you will develop Alzheimer's disease in the future. Scientists have mapped out the entire human genome, and know exactly what base pairs and sequences are present. It doesn't mean that we understand what every gene does, or what genes are present. As we study more people and understand what traits and diseases they have and analyze what genes they possess, we add to the database of genetic knowledge and have a better understanding of what these genes do."


How Someone Physically Healthy like Chris Hemsworth can be at Risk for Alzheimer's

Chris Hemsworth doing pushups

Dr. Yashar says, "It's hard to say why Chris is at higher risk for developing Alzheimer's without knowing the details of his medical history and genetic testing. However, it's possible that if his grandfather was diagnosed with Alzheimer's and both his grandfather and Chris carry similar DNA makeup, then his risk for developing Alzheimer's could be elevated. Depending on the genetic test that was performed, having an increased risk does not necessarily mean he will develop Alzheimer's which is why he is maintaining an extremely positive outlook."

Dr. Mesiwala states, "Chris Hemsworth may epitomize what a healthy person looks like, with his physique and lifestyle. The fact that he carries certain genes may not manifest in any symptoms at the present time. Some of his genes, which give him blonde hair, or other physical traits, manifest during development of the fetus, and growth of a child.. Other genes, like the APOE-4 gene that he was found to have two copies of, are present in some people who have Alzheimer's disease. Those genes may not cause Alzheimer's disease, but are associated with people who have the disease. In other words, he may never develop Alzheimers, but should take steps to try to minimize the risks of developing the disease in the future. We know that there are steps that people can take to keep their brain healthy, their minds active, and environment stimulating in order to allow for continued brain growth and development throughout adulthood, minimizing memory loss, which may, in turn, help reduce the development of dementia and Alzheimer's disease."

Dr. Cox says, "Chris Hemsworth found out that he was more at risk for Alzheimer's disease after finding that he had 2 copies of the APOE4 gene.  His healthy lifestyle can greatly help reduce his risk but will not change his genetic makeup.  Alzheimer's disease showing up in someone's life happens as a consequence of genetics and lifestyle.  We know that certain genes, such as the APOE4 gene, and certain lifestyle factors can greatly increase a person's risk for Alzheimer's disease. Participants with a high genetic risk and an unfavorable lifestyle were more than three times more likely to develop dementia compared with those with a low genetic risk and favorable lifestyle. The risk of any dementia was more than halved among participants with a high genetic risk following a healthy lifestyle compared to those with an unhealthy lifestyle.  We know in studies the power of lifestyle is very significant, decreasing risk for Alzheimer's by 60% even for individuals who are high risk."


A Positive Attitude Makes a Difference


Hemsworth is approaching the shocking news with a positive mindset and said, 

"If you look at Alzheimer's prevention, the benefit of preventative steps is that it affects the rest of your life. When you have preposition to cardiovascular heart disease, cancer, anything—it's all about sleep management, stress management, nutrition, movement, fitness. It's all kind of the same tools that need to be applied in a consistent way.

According to Dr. Yashar, "As with any medical condition, it's always important to focus on the positives rather than the negatives. Having a risk factor does not mean that you will develop a medical condition, especially if those risk factors are "modifiable."  It's critical to be proactive about any medical condition, and do what it takes to reduce those risk factors when possible. It's important to continue to keep your mind active (such as reading, learning, socializing with friends and others), get about 7-8 hours of sleep on a nightly basis, to eat a healthy and well-balanced diet, as well as minimize those risk factors for stroke (such as high blood pressure, high cholesterol, diabetes, etc)." 

Dr. Mesiwala shares, "While there is obvious value in genetic testing, the emotional and psychological impact of finding out that you have an increased risk of developing a disease or will develop a certain disease can be life changing. Having a positive mindset and outlook is critical in being able to manage this information. All the steps that Chris Hemsworth is taking will ultimately lead to a healthier lifestyle, lower his risk of developing many diseases in the future, and generally have a positive impact on his life and his family's life. There is no downside to what he is doing. The same holds true for anyone who has information from genetic testing. The risk is that some people may not understand that the presence of certain genes may mean an increased risk of developing something, but it may never lead to problems. In other situations, the presence of certain genes is 100% associated with the development of certain cancers or degenerative processes. In these people, having proper medical guidance can be life-changing, and essential to receiving proper care and attention."

Dr. Cox says the preventive measures Hemsworth is taking are "crucial.  His quote is perfect because it is true!  The hope would be for anyone who has this testing done to take the results and address any risk factors that are present.  Mindset is so important as stress management is a piece of the puzzle and we want to address the risk and keep living life and not have the result lead to an unhealthy amount of anxiety that may detract from the quality and the length of someone's life."


Genetic Testing Gives the Opportunity to Take Preventive Measures You Might Not Have Before

Moody aged man feeling unhappy.

Dr. Yashar emphasizes, "There is no doubt that an ounce of prevention is more important than a pound of cure. Depending on the medical condition or situation, it's imperative that you be proactive in addressing the various risk factors for that condition, especially those that are modifiable. Although addressing those risk factors may not necessarily prevent you 100% from developing the condition, it will lower your risk for the condition."

Dr. Mesiwala says, "Having genetic information that shows that you will develop a certain disease or have an increased risk for developing a certain disease, can save a person's life, positively impact decision making for their family and future, and provide time that they might otherwise not have. A concrete example includes the presence of a certain mutation of the BRCA gene, which is associated with an increased risk of breast cancer and ovarian cancer in men and women. People who carry these genes should seek medical attention, as many people will undergo surgery, such as the removal of breast tissue, in order to prevent the development of cancer and save their life. In patients with Huntington's disease, the gene responsible for this can be readily identified, and if present, might lead a person to decide against having kids in order to prevent this disease from being passed on to future generations. In Chris Hemsworth's case, he has demonstrated that finding out that he carries a gene which may increase his risk of developing Alzheimer's disease, has caused  him to refocus the priorities in his life, modify his 

lifestyle, and take steps to minimize the risk of developing Alzheimer's disease in the future."

Dr. Cox says, "It is hard to describe how important the information of genetic testing is for each individual.  For the most part, what I see in practice is a feeling that people will live long lives and discount the daily unhealthy behaviors.  If someone would change their current lifestyle to healthier habits by knowing they are more at risk, this would be beneficial.  For some people, anxiety around this knowledge may lead them to not get the genetic test done in the first place. There is a lot that we can do to reduce the risk of Alzheimer's disease.  I say this because the typical American lifestyle – high stress, inadequate sleep, sedentary, and poor nutrition – is not aligned with health and greatly increases our risk of multiple lifestyle diseases including increasing our risk for dementia.  Nutrition is a huge piece and it is well known that a diet high in fruits and vegetables, beans and lentils, whole grains, nuts and seeds can decrease our risk for dementia, even if we are genetically predisposed."   


What to Know About Alzheimer's

21 Ways to Prevent Memory Loss

Dr. Yashar says, "Alzheimer's disease, and dementia in general, are medical conditions affecting how your brain works. One of the most common initial signs of Alzheimer's disease is memory loss that affects or disrupts your everyday life. Other signs include difficulty remembering how to perform routine tasks or planning or solving routine problems. Your ability to remember where you are or what's the day/date can also be an early sign of someone with Alzheimer's."

Dr. Mesiwala explains, "Alzheimer's disease is a type of dementia  that affects memory, thinking, and behavior. It is a progressive condition that worsens over time, and eventually affects every activity of daily life. The disease accounts for the majority of dementia cases in the United States. It is more common the older one is. Very rare, familial forms of Alzheimer's disease occur in people who are in their 40s and 50s. Patients with Alzheimer's disease may live 4-8 years after diagnosis. In some patients, depending on certain factors, and with intervention, including medication, lifestyle changes, and cognitive therapy, survival may be up to 20 years after diagnosis. While many advances have been made in the diagnosis and treatment of Alzheimer's disease, there is currently no cure. Early warning signs of Alzheimers include memory loss that affects daily life, challenges in planning and solving problems, difficulty completing familiar tasks, confusion, with time or place, trouble understanding visual images and spatial relationships, new problems with the words in writing and speaking, misplacing things, and losing the ability to retrace steps, decreased, or poor judgment, withdrawal from work or other social activities, and changes in mood and personality."

Dr. Cox states, "I'd like to stress the importance of our day-to-day lifestyle choices.  Often we get busy and are focused on work, schedules, finances and the attention to our own wellbeing takes a backseat. People often think that healthy foods are expensive but beans and brown rice or other healthy options are often less expensive than the unhealthy alternatives.  Oxford University did a study on the cost of plant-based diets versus the standard American Diet and found that plant-based diets are less expensive.  For people that choose to get the genetic test, it is important to keep in mind that even if someone has zero copies of the APOE4 gene, people can still get Alzheimer's dementia or other dementia – the risk greatly increases with unhealthy lifestyles.  To say it differently, if the test is negative, it does not mean that someone is "safe" from Alzheimer's dementia."

Heather Newgen
Heather Newgen has two decades of experience reporting and writing about health, fitness, entertainment and travel. Heather currently freelances for several publications. Read more about Heather