While working on a Disney+ documentary that will unravel the mysteries of longevity, Chris Hemsworth underwent a series of genetic tests to see what, if anything, the future might hold for him.
But what the Avengers actor discovered, he said on National Geographic-supported series Limitless, was “my greatest fear.”
The 39-year-old star was found to have two copies of the APOE4 gene, one from his mother and the other from his father. Some studies have linked this combination to a 10-fold increased risk of Alzheimer’s.
Now he’s said to be taking a big step back from Hollywood movies and taking on fewer acting roles, according to the news.
Alzheimer’s affects around 850,000 people in the UK and 5.8 million in the US, but the charity figure fears charitable rates will rise in the coming decades as the world population ages.
Chris Hemsworth, pictured above, has two copies of the APOE4 gene found, one from his mother and the other from his father, which studies have linked to an increased risk of Alzheimer’s
About 75 percent of people have the APOE2 or APOE3 of the APO gene, while 20 percent have a copy of APOE4 — the dementia gene. Between 3 and 5 percent of people have two copies. The e4 variant is associated with an increased risk of Alzheimer’s disease, while APOE3 appears to have no effect and APOE2 may even provide protection against the disease. People born with a copy of the e4 strain have a double risk of developing Alzheimer’s between the ages of 65 and 80. Scientists estimate that people with two copies have a 10- to 15-fold increased risk of developing Alzheimer’s after the age of 65
It is the most common form of dementia, accounting for between 60 and 80 percent of all cases.
So what are the genetic tests? where to get one And are there other ways to find out if you’re at risk for Alzheimer’s?
Here Web explains everything you need to know.
What is the APOE gene?
According to the Alzheimer’s Society, the development of the disease has not been directly linked to a single genetic change.
But over the past few decades, nearly 20 different genes have been identified that may play a role.
One, called the APOE gene, is the strongest known genetic risk factor for Alzheimer’s.
Everyone has two versions of the gene – one from their mother and one from their father.
Around 75 percent of people have the APOE2 or APOE3 variants, which are not associated with the cruel disease. Some studies even suggest a protective effect.
About 20 percent have one copy of APOE4, while between 3 and 5 percent of people have two copies.
Leading scientists in the field of neurology estimate that between 40 and 65 percent of people diagnosed with Alzheimer’s have the APOE4 variant, whether it’s just one or two copies.
But they insist that those who inherit two copies of the APOE4 variant will not definitely develop Alzheimer’s.
The gene influences the risk of developing Alzheimer’s disease, but is not a cause.
Researchers believe there is no single cause of Alzheimer’s. Instead, it likely develops from multiple risk factors, including genetics, lifestyle, and environment.
Genetic Test Kits
The most widely used DNA APOE genetic testing kits come from the genetic testing company 23andme.
It will cost you £149 and is available either online or from some high street pharmacies including Boots and works with a saliva swab which is then sent to a testing lab.
In 2013, the US Food and Drug Administration (FDA) banned 23andme from marketing its genetic test as a medical product because the company failed to provide the agency with information supporting its marketing claims.
However, they were still allowed to offer their ancestral service.
In 2017, the company received FDA approval to recommercialize reports of genetic health risks of Alzheimer’s, Parkinson’s and late-onset hereditary thrombophilia in the United States along with their other reports.
The Medicines and Healthcare Products Regulatory Agency (MHRA), which oversees the safety of medicines used in the UK, also warned against using the product with caution after it was approved in the UK in 2014.
Alzheimer’s experts are still divided on whether testing for the gene is helpful for most people.
For this reason the test is not available on the NHS. Only those who have an apparent family history and a pattern of Alzheimer’s affecting each generation at a young age may be eligible for similar diagnostic genetic testing, which involves a blood test to confirm that someone has mutations in the PSEN1, PSEN2 or APP genes.
“People who get results that confirm they don’t have APOE4 will assume they won’t get Alzheimer’s,” the Alzheimer’s Association warned.
“The truth is these people may still be at risk due to lifestyle and environmental factors, as well as other genetic variants that are not accounted for by this test.”
Meanwhile, the Alzheimer’s Society said, “These kits cannot tell the full story of a person’s risk of developing the disease.”
How reliable are they?
The tests are delivered to people’s homes, where they spit into a test tube and send it to a lab for analysis — no blood or needles needed.
Four to six weeks later, a report written in everyday language comes in the mail. With results for over 150 reports, in addition to Alzheimer’s, it also provides reports on the genetic risk of developing diseases such as Parkinson’s, type 2 diabetes and chronic kidney disease.
It also includes results from pharmacogenetic tests, which provide information about how certain medicines interact with your body and genetic makeup.
But the results aren’t always as accurate as they seem.
“This test can produce false positive or false negative results,” 23andMe noted in its summary of test performance.
While the company says its reports are 99 percent accurate, it recommends seeking genetic counseling before and after taking the test to understand the results and possible options.
“Genetic health risk reports are designed to provide you with genetic information to engage in discussions with a doctor,” he added.
“These reports should not be used to make medical decisions. Always consult a doctor before taking any medical action.”
The most widely used DNA APOE genetic testing kits come from the genetic testing company 23andme. It will cost you £149 and is available either online or from some high street pharmacies including Boots and works with a saliva swab which is then sent to a testing lab
The APOE gene — important for making a protein that helps move cholesterol through the bloodstream — is the gene most associated with Alzheimer’s. Everyone has two versions of the gene, one from their mother and one from their father. The APOE4 variant is associated with an increased risk of developing Alzheimer’s, while APOE3 appears to have no effect and research suggests that APOE2 may even provide protection against the disease
Other ways to detect Alzheimer’s
hearing tests
Regular hearing tests, especially in people in their 30s and 40s, could provide early clues to Alzheimer’s, experts have suggested.
Earlier this year, researchers said other risk factors, including social isolation or depression, could be reduced by treating potential hearing loss earlier and using hearing aids.
Meanwhile, previous research found that hearing aid wearers had a 50 percent lower risk of mild cognitive impairment than those who did not use them, while another showed they could reduce the progression from mild cognitive impairment to dementia by 27 percent.
Yet the stigmas associated with hearing aids and the difficulties in accessing them mean that most people who need them still don’t use them.
In 2017, the Lancet Commission on Dementia also discovered that 12 modifiable risks – one of them hearing loss – could reduce the number of dementia cases by 40 percent.
What is the Hemsworth dementia gene?
A person receives one version of the APO gene, a protein scientifically called apolipoprotein E, from each parent at conception. There are three types of the protein: e2, e3, and e4.
APO is one of more than 20,000 genes that a person develops in the womb. Everyone has two copies of each gene, which they inherit from each of their parents.
All versions of APO are responsible for regulating the way the body transports lipids and cholesterol throughout the body.
About 75 percent of people have e2 or e3 strains, while 20 percent have one copy of e4, and between 3 and 5 percent of people have two copies.
The e4 variant is associated with an increased risk of developing Alzheimer’s disease, while e3 appears to have no effect and e2 may even provide protection against the disease.
People born with a copy of the e4 strain have twice the 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 age 65, scientists estimate.
Others were physical inactivity, obesity and low educational attainment.
eye exams
To diagnose Alzheimer’s, doctors currently use MRI, CT, and PET scans, which evaluate your organ and tissue functions.
But they are invasive and often expensive procedures.
A 2018 study of 32,000 participants found that a simple eye test performed by optometrists could help predict who is at risk of dementia.
People with a thinner retina are more likely to have problems with memory and reasoning, researchers said.
Several studies have also shown changes in the retina in people with Alzheimer’s or other forms of dementia – specifically changes in the layers of the retina due to changes in the blood vessels.
Changes in blood flow and damage to vessel density in the eye can be an indicator of problems with blood flow to the brain, indicating risk of regression from Alzheimer’s disease.
While there are currently no eye tests to help diagnose Alzheimer’s, researchers believe the results of these studies should lead to the development of imaging techniques that allow for earlier diagnosis and treatment.
blood tests
Most patients receive an Alzheimer’s diagnosis only after they develop memory problems.
But an early sign of the disease comes from clumps of a protein called amyloid beta that build up in the brain.
Blood tests are the great hope that one day people will be screened for early signs of Alzheimer’s, as is currently done for early-stage cancer.
And last year, research found that a blood test that detects these toxic lumps was able to identify all but one in 147 people with Alzheimer’s disease.
The test, called the soluble oligomer binding assay (SOBA), needs to be tried in far more people and is still in its early stages.
But Valerie Daggett, a professor of bioengineering at the University of Washington who developed the test, said at the time: “What clinicians and researchers wanted is a reliable diagnostic test for Alzheimer’s disease.
“And not only a test that confirms the diagnosis of Alzheimer’s, but also can detect signs of the disease before cognitive impairment sets in. What we show here is that SOBA can be the basis of such a test.
Earlier this year, research from the Institute of Psychiatry, Psychology and Neuroscience at King’s College London also developed a blood-based test that could predict risk of the condition.
The study supports the idea that components in the blood can influence the formation of brain cells.
Risk factors for behavioral changes
The risk of developing Alzheimer’s disease is complex and involves factors other than genetics.
By far the strongest risk factor is age, with the likelihood of being affected increasing with age.
Other risk factors include diet, exercise, smoking, alcohol consumption and depression.
But there are also dozens of subtle behavioral changes that can also indicate the cruel life-stealing condition.
According to a 2017 report in the Journal of Neurology, Neurosurgery and Psychiatry, people with early dementia laughed less at their own jokes and at others’ funny comments than those who didn’t.
This followed a 2009 report that people with neurodegenerative disease images after MRI scans were less able to detect sarcasm.
The researchers said more studies are needed to determine the exact cause of the changes in humor, but most behavioral changes after developing Alzheimer’s are caused by the brain shrinking in the frontal lobe.
Meanwhile, research from 2011 in the General Psychiatry Archives found that symptoms of clinical depression doubled the risk of cognitive impairment in older women and quadrupled it in men — and could even be a precursor to Alzheimer’s.
Because the symptoms of Alzheimer’s disease progress slowly, it can be difficult to identify a problem.
Many people believe that memory problems, usually the first sign of Alzheimer’s disease, are simply a part of getting older.
According to the NHS, those concerned about possible symptoms they might be showing should first arrange tests with their GP.
What is Alzheimer’s?
Alzheimer’s disease is a progressive, degenerative brain disease in which the buildup of abnormal proteins causes nerve cells to die.
This disrupts the transmitters that transmit messages and causes the brain to shrink.
More than 5 million people have the disease in the US, where it is the sixth leading cause of death, and more than 1 million Britons have it.
WHAT HAPPENS?
When brain cells die, the functions they provide are lost.
These include memory, orientation and the ability to think and reason.
The course of the disease is slow and insidious.
On average, patients live five to seven years after diagnosis, but some can live 10 to 15 years.
EARLY SYMPTOMS:
- loss of short-term memory
- disorientation
- behavior changes
- mood swings
- Difficulty handling money or using the phone
LATER SYMPTOMS:
- Severe memory loss, forgetting close family members, familiar objects or places
- Anxious and frustrated with inability to understand the world, leading to aggressive behavior
- Eventually lose the ability to walk
- May have trouble eating
- The majority will eventually require 24-hour care
Source: Alzheimer’s Association