Actor Chris Hemsworth Just Learned He Has 8X Greater Chance of Getting Alzheimer’s– How Valuable Is Genetic Testing For Major Diseases?

Chris Hemsworth, 39, has been working on a docuseries with National Geographic called “Limitless.” And during the show’s fifth episode, a doctor tells the Thor star that he has two copies of the gene APOE e4 a gene that increases the risk of Alzheimer’s and is associated with getting the disease at an earlier age, according to the Mayo Clinic. The Mayo Clinic also reports that about 15 to 25 percent of the general population carries an APOE e4 allele.

“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,” Hemsworth said in a recent interview. “And 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.”

The Mayo Clinic says “having at least one APOE e4 gene increases your risk of developing Alzheimer’s disease two- to threefold.” But having two APOE e4 genes makes your risk even higher “approximately eight- to twelvefold.” And Hemsworth does, in fact, have a family history of the disease as his grandfather has Alzheimer’s.

“The show, which initially was an exploration of longevity and, of course, should be fun, became even more relevant and important for me, even more poignant than I ever thought it would be,” Hemsorth said. “It was a really good catalyst to dive into everything I needed to be doing in either the prevention front or the management front or however you want to classify it. It’s not a pre-deterministic gene, but it is a strong indication.”

Hemsworth made it clear that the news does NOT mean he’s “been handed [his] resignation.”

“My concern was I just didn’t want to manipulate it and overdramatize it, and make it into some sort of hokey grab at empathy, or whatever, for entertainment,” the father of three and wife to model Elsa Pataky, 46, 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, anythingit’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.”

Understanding Genetic Testing

Genetic testing can provide people with greater knowledge to work with when considering their risk for certain diseases like Alzheimer’s. And it can also do the same for cancer.

With breast cancer, for example, gene mutations of the PALB2, BRCA1, BRCA2, ATM, TP53, CHEK2, PTEN, CDH1 and STK11 genes can lead to inherited breast cancer.

Should I Get Genetic Testing to Assess My Risk for Breast Cancer?

It’s important to note, however, that BRCA and PALB2 mutations are much more common and can increase a person’s risk of breast cancer more than the others mentioned. If a parent carries a BRCA gene mutation, there's a 50-50 chance you could be carrying it too.

Dr. Julie Rani Nangia, an assistant professor at Baylor College of Medicine, previously told SurvivorNet about 10 percent of patients who undergo genetic testing will test positive for the BRCA1 or BRCA2 gene, but an additional 5 to 6 percent will test positive for other genes.

RELATED: Genetic Testing: What Is It and Why Is It Important? An Interview with Breast Cancer Previvor Erika Stallings

About 10 percent of breast cancers are hereditary, accroding to Dr. Ophira Ginsburg, the senior advisor for Clinical Research at the National Cancer Institute's Center for Global Health. So, she recommends genetic testing usually only for women who have a family history of rare cancers, family members with breast or ovarian cancer and other cancers associated with the Lynch Syndrome (a genetic condition that puts you at high risk for certain cancers) or a family history of common cancers diagnosed at a young age.

Inherited Genetic Disorders in Colon Cancer: FAP

Other cancers like colon, pancreatic and ovarian cancer which can have hard-to-spot symptoms can sometimes be detected earlier with genetic testing. And this generally means better treatment outcomes.

Given that a patient with pancreatic cancer does not always have the best prognosis, Jessica Everett, a genetic counselor at NYU Langone's Perlmutter Cancer Center, suggests people with a family history of the disease take action to assess their risk level.

"If you're concerned about pancreatic cancer in your family, start by talking to a genetic counselor to learn more about your risk and what options you have," Everett told SurvivorNet.

Genetic testing can be used for preventative measures, but it can also be very helpful in navigating treatment options after a cancer diagnosis. With ovarian cancer, for example, BRCA 1, BRCA 2, PALB2, ATM gene mutations can point doctors toward PARP inhibitors which work by preventing cancer cells from repairing their own damaged DNA.

Genetic Testing Can Help Guide Ovarian Cancer Treatment Decisions

"Certain individuals with ovarian cancer, if they proceed with genetic testing and they test positive in specific genes, they might benefit the most from having PARP inhibitor medicine prescribed for them as treatment for their ovarian cancer," says Lauren Mills, a genetic counselor at UT Health San Antonio, adding that women who test negative for mutations in these specific genes may also benefit from PARP inhibitors.

How Genetic Testing Determines Treatment in Lung Cancer

And when it comes to lung cancer, genetic testing can reveal the presence of certain genetic mutations including KRAS, ALK, EGFR and a number of others which can help doctors tailor treatment for each person's specific disease.

Overall, genetic testing can be a great way to better understand your risk of developing certain cancers as well as best potential treatment options if you've been diagnosed with a certain cancer. But people should be aware that direct-to-consumer genetic testing companies like 23andMe do not give you the in-depth genetic analysis needed to fully understand your cancer risk.

Buyer Beware: Direct-to-Consumer Genetic Testing

Dr. Ginsburg says the tests can identify BRCA1 and BRCA2 mutations in Ashkenazi Jews at a very superficial level, for instance, as they test only a fraction of the genes' thousands of mutations. Dr. Ginsburg warns “buyer beware” because you could end up with a false sense of reassurance.

“For this reason, we really encourage people to seek proper genetic counseling from a certified genetic counselor, even if it’s a commercial laboratory that can provide such a service over the phone,” Dr. Ginsberg said, adding that insurance companies will likely cover the genetic tests done by a healthcare professional if you’re a high-risk profile for breast cancer.

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