Playing sport could ‘re-awaken dormant viruses in the brain and trigger Alzheimer’s disease’
PLAYING a sport could re-awaken dormant viruses in the brain and trigger Alzheimer’s disease, a study says.
Oxford scientists found evidence that viruses such as the cold-sore virus could “wake up” and cause harmful changes to brain cells.
For a long time, a connection between head injuries – including those in sport – and dementia has concerned the sporting industry.
Studies have shown that repeated head injuries, such as concussions, can lead to the build-up of proteins in the brain called tau, which disrupts normal function and leads to dementia symptoms.
But it’s not until now that researchers from Oxford’s Institute of Population Ageing and the University of Manchester have suggested this may be triggered by a chain reaction that could start with just a mild brain trauma.
In previous studies, the researchers demonstrated the roles that common viruses, such as herpes simplex virus type 1 (HSV-1) – the so-called cold sore virus – and varicella zoster virus (VZV) – which causes chickenpox and shingles – play in the development of Alzheimer’s.
HSV-1 can lie dormant in human cells for a lifetime, but when it re-awakens it can cause changes that resemble changes observed in Alzheimer’s patients’ brains.
This includes amyloid plaque-like formations (PLFs), gliosis, neuroinflammation, and decreased functionality.
In the latest study, published today in Science Signaling, the researchers used a small, 3D, bioengineered human brain tissue model to test the effects of physical trauma on the brain cells.
When the brain tissues were exposed to repeated “mild blows,” similar to concussions, the previously dormant HSV-1 virus became active.
This reactivation triggered inflammation, beta-amyloid plaque build-up, and the formation of harmful tau proteins, which can damage brain cells and impair memory.
By blocking an inflammatory molecule called Interleukin-1 beta (IL-1β), many of these harmful effects were prevented in lab models.
It offers hope for potential new treatments for those at risk.
Professor Ruth Itzhaki, who led the research, has been researching the potential role of HSV-1 in AD for more than 30 years.
She said: “Head injuries are already recognised as a major risk factor, as are the cumulative effect of common infections, for conditions such as Alzheimer’s and dementia, but this is the first time we have been able to demonstrate a mechanism for that process.
“What we’ve discovered is that in the brain model these injuries can reactivate a dormant virus, HSV1, setting off inflammation which, in the brain, would lead to the very changes we see in Alzheimer’s patients.
“Understanding both the risk factors for dementia and Alzheimer’s, and the mechanism by which they develop, is important in being able to target treatment and prevention at as early a point as possible.”
The researchers hope their work will pave the way for new treatments to protect against neurodegeneration, particularly for those at high risk due to repeated concussions.
Other infections that are linked with Alzheimer’s, according to Alzheimer’s Society, are herpes, pneumonia, syphilis, Lyme disease and gum disease.
Research shows that dementia is more common in people who have these infections.
The charity says that exercise is one of the best ways to reduce the risk of dementia, including sports like rugby and football.
“However, while researchers work to understand this important issue, contact sports must be played as safely as possible,” it warns.
Several high-profile sports players have battled dementia.
The family of footballer Nobby Stiles, part of the England’s 1966 World Cup-winning team, believe that his dementia was linked to his career, particularly heading the ball. He died aged 78 in 2020.
From the same team, Sir Bobby Charlton’s diagnosis and death in 2023, aged 86, has also been part of a broader conversation about the impact of heading the ball.
American football player Mike Webster, meanwhile, was one of the first high-profile cases of Chronic Traumatic Encephalopathy (CTE), a condition linked to repeated head traumas.
He died aged 50, in 2002, and his struggles with dementia and other cognitive issues were chronicled in the film “Concussion”.
Alzheimer's disease symptoms
Alzheimer’s disease is the most common cause of dementia in the UK.
The symptoms progress slowly over several years.
Sometimes these symptoms are confused with other conditions and may initially be put down to old age.
And the rate at which the symptoms progress is different for each individual.
In the early stages, the main symptom of Alzheimer’s is memory lapses.
For example, someone with early Alzheimer’s may:
- forget about recent conversations or events
- misplace items
- forget the names of places and objects
- have trouble thinking of the right word
- ask questions repetitively
- show poor judgement or find it harder to make decisions
- become less flexible and more hesitant to try new things
If you’re worried about your memory or think you may have dementia, it’s a good idea to see a GP.
Source: NHS