Chris Hemsworth revealed on Friday that he has two genes that put him at a much higher risk of Alzheimer’s disease than the average person, but neurologists tell The Daily Beast that’s not necessarily cause for alarm.
The revelation came during a recent episode of Hemsworth’s National Geographic series Boundlessairing on Disney+, which claims to offer “fascinating insights into how we can all unlock our bodies’ superpowers to fight disease, perform better, and even reverse the aging process.”
In episode five, entitled “Memory”, Dr. Peter Attia the Australian actor that he has two copies of the APOE4 gene, one from his mother and one from his father. This, Attia says, makes him up to 10 times more likely to develop Alzheimer’s disease compared to the average person. Hemsworth reacts glumly to the news as he adjusts his posture and focuses intently on the doctor’s words. During a confessional filmed afterwards, he says he was “floored”.
The information was apparently so sensitive that Attia called Boundless creator Darren Aronofsky to tell him he would rather break the news privately rather than on camera, Hemsworth told Vanity Fairadding that the whole thing was “pretty shocking”.
Only about 2 to 3 percent of people have both copies of the gene, says Dr. Corinne Pettigrew, the leader of outreach, recruitment, and engagement at the Johns Hopkins Alzheimer’s Disease Research Center.
And it doesn’t mean Hemsworth is guaranteed to get the disease.
For starters, a crash course on the gene can be helpful. The gene for Apolipoprotein E, or APOE, tells your body how to make the protein of the same name, which helps metabolize fat and transport cholesterol around your body. The gene comes in variations, or alleles, APOE2, APOE3, and APOE4.
The APOE4 gene carries the “worst possible risk for Alzheimer’s disease,” says Dr. Lawrence S. Honig, professor of neurology at Columbia University and director of the New York State Center of Excellence for Alzheimer’s Disease.
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“It’s true that having one or two APOE4 increases the risk, but it’s inconclusive, so we don’t usually find it useful to test for it except in a research setting,” Honig tells The Daily Beast.
Both Honig and Sam Gandy, a professor of neurology and the director of the Mount Sinai Center for Cognitive Health, emphasize that there is a large proportion of Alzheimer’s patients — anywhere from a third to a half — who have no APOE4 genes at all.
“Not everyone with two copies will develop Alzheimer’s,” says Gandy. “There are rare people who escape it. Diet and lifestyle are important.”
Also important is resistance to the gene’s worst effects, some of which appear to be possessed in greater amounts than others. “They could be carriers of what we call resilience genes,” says Gandy.
While the exact link between APOE4 and Alzheimer’s disease has not been established, studies show links between the gene and the buildup of amyloid plaques and tau tangles, both widely considered telltale signs of Alzheimer’s disease. The gene also disrupts the blood-brain barrier. “It is important that proteins in the blood are separated from proteins in the brain. People with this gene have a leaky blood-brain barrier,” explains Gandy. In addition, APOE4 is believed to make the protein that helps transport cholesterol. The myelin, an insulating layer that allows nerve cells to develop electrical properties to communicate with each other, requires a lot of cholesterol. The gene can “impair” the amount of cholesterol the myelin receives, says Gandy. A fourth connection is that APOE4 genes stimulate inflammation.
But because the disease is so tied to your genetic makeup, Honig wouldn’t recommend anyone take a test like Hemsworth’s.
“What should he do with that information?” says Honey. “The answer is he can’t do much with that information because he doesn’t know whether or not he’s going to get that disease, and we don’t have a clear way to prevent Alzheimer’s disease at this point.”
Pettigrew agrees. Although she has seen estimates that say the risk for patients with two APOE4 alleles is 10 times greater than for people who don’t have them, “there’s nothing we can do right now, as far as we know, that would definitely stop or prevent dementia.”
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For Hemsworth, Marvel’s star Thor franchise, the news that he carried two APOE4 alleles was all the more distressing considering that his grandfather is currently living with the incurable disease.
“I’m not sure he remembers much more and he slips in and out of Dutch, which is his native language, so he’ll talk Dutch and English and then a mix and maybe some other new words. ”, said the 39-year-old Vanity Fair.
Hemsworth says the news, and the show in general, forced him to reconsider his lifestyle and take a step back. He now plans to complete his remaining contracts and take “a chunk of time off” and just simplify it.
Overall, doctors agree that positive lifestyle changes, such as a healthy diet, exercise, and regular social interaction, can help a person avoid the worst effects of Alzheimer’s disease and other dementia-related illnesses, even if the risk seems high.
“Even if you can put it off by 10 years, that’s a huge increase in cognitive and functional time you have,” says Pettigrew.
Honig adds that some of the drugs currently being worked on also offer some hope. One drug in particular shows that people with APOE4 could benefit more from taking it.
“Having APOE4s — one or two — increases the amount of amyloid protein in the brain in general, as well as in the blood vessels,” says Honig. “If you have more amyloids, the antibodies give you more side effects, but in the same way that you get the side effects, it may mean that the antibody is working better on the amyloid.”
There’s hope, but until these drugs are more thoroughly researched and reach a wider market, “you’re kind of stuck with your genes,” says Honig.
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