Chris Hemsworth revealed Friday that he has two genes that put him at a much higher risk of developing Alzheimer’s disease than the average person, but neurologists tell The Daily Beast that’s not necessarily cause for concern.
The revelation came during a recent episode of Hemsworth’s National Geographic series Limitlesswhich airs on Disney+ and purports to offer “fascinating insights into how we can all unleash our bodies’ superpowers to fight disease, perform better and even reverse the aging process.”
In episode five, entitled “Memory,” Dr. Peter Attia told 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 compared to the average person. Hemsworth reacts somberly to the news as he adjusts his posture and focuses intensely on the doctor’s words. During a confessional filmed afterwards, he says he was “devastated.”
The information was obviously so sensitive that Attia called Limitless Creator Darren Aronofsky to tell him he’d rather break the news privately than on camera, Hemsworth said vanity fairadding that the whole thing was “quite shocking”.
Only about 2 to 3 percent of people have both copies of the gene, says Dr. Corinne Pettigrew, director of public relations, recruitment and engagement at the Johns Hopkins Alzheimer’s Disease Research Center.
And that doesn’t mean Hemsworth is guaranteed to develop the disease.
A crash course on the gene might be helpful for starters. 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 throughout your body. The gene comes in variations or alleles, APOE2, APOE3 and APOE4.
The APOE4 gene carries the “highest 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.
“It’s true that one or two APOE4 does increase the risk, but it’s not conclusive, so we don’t typically find it worth testing except in a research setting,” Honig told The Daily Beast.
Both Honig and Sam Gandy, professor of neurology and director of the Mount Sinai Center for Cognitive Health, point out that a good proportion of Alzheimer’s patients – between a third and half – have no APOE4 genes at all.
“Not everyone with two copies will develop Alzheimer’s,” says Gandy. “There are rare people who escape this. Diet and lifestyle are important.”
Also important is resistance to the gene’s worst effects, which some seem to have in greater amounts than others. “They might carry what we call resilience genes,” says Gandy.
While the exact link between APOE4 and Alzheimer’s has not been established, studies show links between the gene and the formation of amyloid plaques and tau ‘tangles’, both of which are widely regarded as telltale signs of Alzheimer’s. 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. Also, APOE4 is thought to create 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 “affect” how much cholesterol 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 is reluctant to recommend anyone take a test like Hemsworth’s.
“What should he do with this information?” says honey. “The answer is that he can’t do much with this information because he doesn’t know if he’s going to get this disease or not, and we don’t have a clear way to prevent Alzheimer’s disease right now.”
Pettigrew agrees. While she’s 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 that we know of at this point that would definitely stop or prevent dementia.”
For Hemsworth, the star of Marvel Thor franchise, the news that he carried two APOE4 alleles was all the more poignant considering his grandfather is currently living with the terminal illness.
“I’m not sure he can remember much and he’s slipping in and out of Dutch, which is his original language, so he’ll speak Dutch and English and then a mash-up and then maybe another few other new words,” said the 39-year-old vanity fair.
Hemsworth says the news and the show in general forced him to reckon with his lifestyle and take a step back. He now plans to complete his remaining contracts and “take some time off and just simplify.”
All in all, doctors agree that positive lifestyle changes like a heart-healthy diet, exercise, and regular social interaction can help someone stave off the worst effects of Alzheimer’s and other dementia-related diseases, even when the risk seems high.
“Even if you can push it back 10 years, that’s a huge increase in the cognitive and functional time you have,” says Pettigrew.
Honey adds that some of the drugs currently being worked on also offer hope. One drug in particular shows that people with APOE4 may benefit more from its use.
“The presence of APOE4 – one or two – increases the amount of amyloid protein in the brain overall, but also in the blood vessels,” says Honig. “If you have more amyloid, the antibodies will have more side effects, but just as you’re getting the side effects, it may mean the antibody is working better on the amyloid.”
There is hope, but until these drugs are more thoroughly researched and reach a broader market, “you’re kind of stuck with your genes,” says Honig.