Genetic Testing Revealed Chris Hemsworth's Alzheimer's Risk & Here's What It Can Tell You
All it takes is a simple blood test.
Chris Hemsworth at a movie premiere in 2018. Right: An MRI showing a brain scan.
Chris Hemsworth revealed some shocking news to his fans this month, saying he is taking a break from acting after finding out he has a high risk of Alzheimer's disease.
The Thor actor got the news after getting a genetic test done while filming his new Disney+ documentary series Limitless.
In an interview with Vanity Fair, Hemsworth says the test confirmed his "biggest fear" when it comes to the neurodegenerative disease.
Through the test, the actor discovered he has two copies of the APOE4 gene, one from each parent.
While 25% of people carry one copy of APOE4, only 2 to 3% carry two copies, according to a 2021 study by the National Institutes of Health. This genetic makeup is considered "the strongest risk factor gene for Alzheimer's disease."
The 39-year-old actor tells Vanity Fair that he views the results as a "blessing" because he can now work towards managing his risk of Alzheimer's disease.
Following Hemsworth's news, we went looking for information about genetic testing and what experts have to say about having it done.
What is Alzheimer's disease?
The Alzheimer's Association defines Alzheimer's as "a type of dementia that affects memory, thinking and behavior."
The organization says it's the most common cause of dementia, accounting for 60-80% of dementia cases.
What are the symptoms of Alzheimer's disease?
There are a number of warning signs when it comes to Alzheimer's, according to the Alzheimer Society.
Some of these symptoms include memory loss affecting daily life, difficulty doing familiar tasks, trouble finding simple words when speaking and changes in personality.
Dr. Constantine Lyketsos, Elizabeth Plank Althouse professor at Johns Hopkins, says it's important to understand that not all memory problems are an indicator of Alzheimer's.
Someone in their 40s who has memory problems most likely has them because of stress, a lack of sleep or possibly using substances like alcohol more than the brain can tolerate, Lyketsos said.
"If you're talking about an 80-year-old, memory changes that are starting to affect day-to-day functioning, getting lost, having trouble managing medicines, problems driving, those are all things that among others should lead to getting an evaluation by a physician," the doctor told Narcity.
Can Alzheimer's disease be detected through genetic testing?
Lyketsos says genetic testing for Alzheimer's is done with a simple blood test, which is similar to testing done for heritage sites like 23andMe and Ancestry DNA.
The test will determine which version of the APOE gene a person has.
However, Lyketsos also points out that the results of the testing cannot predict for sure if you will or will not develop Alzheimer's disease.
As noted previously, Hemsworth has two copies of the gene APOE4, which is called a "risk-factor gene" because it increases a person's risk of developing the disease, according to the U.S. National Institute of Aging.
"Having two copies is even a higher risk for maybe a slightly younger age of onset," Lyketsos, who did not treat Hemsworth, said. "But there are people who (have two copies) into their 90s who don't get the disease so again, it's not deterministic, it's more of a probabilistic increase in risk."
Should you get tested for this Alzheimer's gene?
While the testing may be simple, Lyketsos says he would not recommend it for everybody for two reasons.
"First the deterministic genes are very, very, very rare so the chances that you carry them are almost zero," he told Narcity. "Second, if you are testing for the [APOE4], like I said, it's not 100% either way.
"So given that you're not going to do anything differently, if you know that you have two copies, you should already be doing all the right things to prevent dementia."
The only instance where he would do the test is when there's a question about a current diagnosis.
How can you prevent having Alzheimer's?
Though research is still ongoing, the Alzheimer's Association says there is strong evidence that shows people can reduce their risk by making lifestyle changes.
Harvard Medical School recommends 30 minutes of moderately vigorous aerobic exercise, three to four days per week.
Eating a Mediterranean diet, which includes fresh fruit and vegetables, whole grains, nuts, legumes and poultry is also advised.
Getting between seven and eight hours of sleep is also important.
Lyketsos says managing diabetes, high blood pressure, obesity, and smoking, are also straightforward things that can reduce a person's risk of Alzheimer's.
"There's also what we call mental and social engagement: [...] socially and mentally be part of the church, be part of other community groups, interact with friends," Lyketsos highlighted in his interview.
What age does Alzheimer's start?
Age is the biggest factor for Alzheimer's disease.
Early-onset Alzheimer's is rare and typically happens between the ages of 30 and mid-60s.
Late-onset Alzheimer's is the more common of the two, with people most often experiencing symptoms in their mid-60s or later.
"It's very uncommon before age 60-65 and by the time you reach 85 or older, you've got about a one in three chance of getting it," Lyketsos said.