Chris Hemsworth has a high Alzheimer’s risk. Should you get tested?

Over the past weekend, actor Chris Hemsworth announced he would take a break from acting after learning he has a genetic predisposition to Alzheimer’s.

The 39-year-old, best known for playing Marvel superhero (and literal god) Thor, underwent a series of genetic tests while filming his new National Geographic docuseries “Limitless,” which seeks to push back against the challenges posed by aging.

Hemsworth learned he has two copies of the gene APOE-e4 — one from his father and one from his mother — which studies have linked to an increased risk for Alzheimer’s disease.

So how can someone find out if they’re susceptible to the memory disorder?

What does it mean?

A predisposition is not a diagnosis.

“Knowing that you have a risk doesn’t mean you’re going to get the disease,” said Stefanie Wardlow, a senior program manager at the Alzheimer’s Association of Florida.

People with certain genetic markers seem to have a higher risk of developing Alzheimer’s.

Everyone inherits a type of APOE gene. APOE-e3 is not believed to impact a person’s risk of Alzheimer’s, and APOE-e2 is actually hypothesized to decrease the risk of developing the memory disorder.

APOE-e4, however, is considered the risk gene for Alzheimer’s.

Researchers estimate that between 40% and 65% of people diagnosed with Alzheimer’s have either one or two copies of the APOE-e4 gene, Wardlow said.

While 1 in 4 people have a single copy of the marker, Hemsworth is among just 2 to 3% of people who have two.

People with at least one of these genes are two to three times more likely to develop Alzheimer’s; people with two are eight to 10 times as likely.

An important caveat here: Genes are only one factor that contributes to a person’s risk. Just because someone lacks APOE-e4 doesn’t mean they’re guaranteed to be safe from Alzheimer’s.

Should I get tested too?

Many biotechnology companies like 23andMe now offer testing for genetic markers — including the APOE-e4 gene.

However, health care providers generally do not recommend routine testing for Alzheimer’s disease in healthy individuals — it’s limited information and can be easy to misinterpret results.

Organizations like the Alzheimer’s Association caution that anyone seeking this information should speak with a genetic counselor before and after undergoing testing.

“Mr. Hemsworth, when he got the results during his film, a doctor actually talked to him about it,” Wardlow said. “That’s what you want, so that if you do have questions, like, ‘What should I do? What does it mean? Can I pass this down to my children?’ You have a safe area to have these conversations.”

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The National Society of Genetic Counselors has a directory of genetic counselors Tampa Bay residents can use to find a doctor in their area.

Is there a way to know for sure?

There are “risk genes” like the APOE-e4. But there are also “deterministic genes” — ones that directly cause Alzheimer’s disease, guaranteeing that anyone who has it will develop the disorder.

These are incredibly rare — scientists have found these genes in only a few hundred families worldwide, accounting for less than 1% of Alzheimer’s cases.

People with these genes usually develop the memory disorder before the age of 65, a condition known as early-onset Alzheimer’s.

People who are showing early symptoms or have a family history of early-onset Alzheimer’s may consider testing for deterministic genes to aid with diagnosis, or to make decisions about family planning or participation in drug trials.

To test for these, contact your local health provider.

What else should I consider?

It’s important to weigh the emotional consequences of genetic testing.

But there are other potential impacts to consider.

The Genetic Information Non-Discrimination Act, or GINA, prohibits use of personal genetic information in employment decisions.

But it does not protect against genetic discrimination in certain forms of insurance, such as disability, long-term care and life insurance, Wardlow said. Test results may affect a person’s eligibility for these types of coverage.

If I’m at heightened risk, what can I do?

Exercise appears to be a strong protective factor against Alzheimer’s disease, studies suggest.

“We really are advocating for individuals to take care of their brain,” Wardlow said.

Healthy eating — though each person should speak with their doctor about what “healthy eating” means for them — as well as socializing and engaging in activities that stimulate multiple parts of the brain at once, such as learning a language or dancing, also appear to reduce the risk of Alzheimer’s.