Avengers star Chris Hemsworth is taking a break from acting after learning he has a genetic quirk that puts him at a much higher risk of developing Alzheimer’s.
While filming a new National Geographic docuseries for Disney+, called Limitless, which explores the impacts of time and age, Hemsworth, 39, took a series of genetic tests.
He learned he had inherited two copies of APOE4, dubbed ‘the Alzheimer’s gene’, from his parents. Studies show that having both copies increases the risk by 10 to 15 times. Having one copy can double a person’s risk.
Many have not heard of APOE4, yet one in five people reading this now are carrying it and between one in 20 and one in 30 have two copies.
The gene is responsible for carrying cholesterol and other types of fat in the bloodstream. Scientists believe the way these genes work can lead to plaques forming in the brain, but have not yet determined why.
Doctors used to believe that carrying two of the gene guarantees a person will develop Alzheimer’s, though more recent research has found that while there are increased risks, they can be offset with a healthy lifestyle.
Dr Stephen Rao, a neuropsychologist at the Cleveland Clinic, told DailyMail.com: ‘‘It does increase your risk [of developing Alzheimer’s], but its not a guarantee.’
Just 150 minutes of moderate exercise a week is likely enough to reduce the heightened risk, according to Dr Ronald Petersen, director of the Mayo Clinic Alzheimer’s Disease Research Center. Moderate exercise includes cycling, swimming, power walking or strenuous gardening.
People used to have to go through hugely expensive genetic blood testing at the doctor’s office to find out if they had two copies of the gene. But at-home tests that cost less than $200 – from companies 23andme and Ancestry.com – mean it is easier than ever before for people to see their genetic make-up.
The tests are delivered to people’s homes, where they spit into a test tube and send it to a lab to be analyzed – without the need for blood or needles. Four to six weeks later, they receive a detailed report in the post written in everyday language.
Around 75 per cent of people have the e2 or e3 of the APO gene, while 20 per cent have one copy of APOE4 – the dementia gene. Between 3 and 5 per cent of people have two copies. The e4 variant is linked to an increased risk of developing Alzheimer’s, whereas e3 appears to have no effect and e2 may even offer protection against the disorder. People born with one copy of the e4 variety suffer a doubled risk of developing Alzheimer’s between the ages of 65 and 80. Those with two copies have a 10 to 15-fold increased risk of developing the disease after the age of 65, scientists estimate
Avengers star Chris Hemsworth (pictured) learned while filming his Disney+ series Limitless that he has the ‘Alzheimer’s gene’. Hemsworth has decided to take time away from acting after the revelation of his genetic risk. Pictured right: The actor in Australia on Monday, spotted for one of the first times since he revealed his genetic risk
A person receives a version of the APO gene, a protein scientifically named apolipoprotein E, from each parent when they are conceived. There are three types of the protein: e2, e3 and e4.
Around 75 per cent of people have the e2 or e3 varieties, while 20 per cent have one copy of e4 and between 3 and 5 per cent of people have two copies.
APO is one of more than 20,000 genes a person develops when they are in their mother’s womb. Every person has two copies of each gene, inheriting one from each of their parents.
All versions of APO are responsible for regulating the way the body transports lipids and cholesterol throughout the body.
The e4 variant is linked to an increased risk of developing Alzheimer’s, whereas e3 appears to have no effect and e2 may even offer protection against the disorder.
People born with one copy of the e4 variety suffer a doubled risk of developing Alzheimer’s between the ages of 65 and 80.
Those with two copies have a 10 to 15-fold increased risk of developing the disease after the age of 65, scientists estimate.
Alzheimer’s is a potentially devastating disease that affects 6.5million Americans. It is the most common cause of dementia.
Alzheimer’s disease is thought to be caused by the abnormal build-up of proteins in and around brain cells. One of the proteins involved is called amyloid, deposits of which form plaques around brain cells.
The other protein is called tau, deposits of which form tangles within brain cells.
Mr Hemsworth told Vanity Fair last week that the shock of discovering his heightened risk made him reevaluate his career.
‘Doing an episode on death and facing your own mortality made me go, “Oh God, I’m not ready to go yet”,’ he said.
But Dr Rao believes that Hemsworth – who stays in notoriously good shape – is overestimating his risk.
He explained that while APOE4 recipients make up around half of Alzheimer’s cases in America, factors like diet and exercise are just as important.
Dr Rao told DailyMail.com the gene affects risk but is not a cause. Other genetic and environmental factors – like weight, diet, sedentary lifestyles and alcohol consumption – are likely to be more influential.
Dr Stephen Rao (left), a neurologist at the Cleveland Clinic, told DailyMail.com that the risks of the Alzheimer’s gene can be mitigated. Dr Ronald Petersen (right), director of the Mayo Clinic Alzheimer’s Disease Research Center recommends seven to nine hours of sleep each night and at least 150minutes of aerobic activity each week to fight Alzheimer’s
A wealth of studies have shown that regular exercise can significantly reduce the risk of developing dementia, by up to 45 per cent for Alzheimer’s specifically.
Limiting sugar and cholesterol levels can significantly reduce Alzheimer’s risk as well.
Diabetes and hypertension, both diseases tied to poor diet and exercise habits, are two of the biggest known risk factors for the cognitive disease.
The doctor continues that sleep is one of the most underestimated tools for keeping the brain healthy. He recommends between seven to nine hours of sleep each night.
He also says elderly people should also keep their brain active by maintaining their social networks.
This is the case for many chronic conditions, where a person can be genetically pre-disposed to it but still manage to avoid the disease by making proper lifestyle choices.
For example, heart disease and type 2 diabetes are both condition where genetics play a strong role in a person’s risk of suffering them – but diet and exercise can mitigate the risk and even prevent the development all together.
Dr Rao said that while finding out a person is at an increased risk of Alzheimer’s can be jarring, a majority of people take it well.
As a part of his research into APOE4 and its effects on the brain, Dr Rao often has to inform patients himself that they have the Alzheimer’s gene.
He said it ‘doesn’t result in major psychological despair for people’ too often’, and he even described Mr Hemsworth’s reaction as ‘extreme’.
Advancements made in recent years make it easier than ever for a person to find out these results as well.
Previously, a person would usually have to take an expensive genetic test at the doctors office to find out if they had a genetic risk for Alzheimer’s.
But now, cheaper at home tests exist that a person can take themselves.
Companies like 23andme and Ancestry.com have risen to prominence in the US in recent years, even receiving regulatory approval for their genetic tests.
While many use them to find a breakdown of their ethnic ancestry, they can also give a person their genetic profile and inform them on what risks they may suffer from.
The tests are relatively cheap as well, usually costing less than $200 each.
Dr Rao says he is ok with use of these tests, but does warn that counseling is not available for a person who finds out they may suffer a devastating disease through these at home tests – while it would be available at a doctor’s office.