Research shows that dormant viruses lurking in the brain can be activated by head injury and cause Alzheimer’s disease.
Studies have long warned that concussions and blows to the head can increase the risk of neurodegenerative diseases.
But now scientists believe such injuries can “awaken” dormant viruses in the brain, causing inflammation and longer-term damage that leads to dementia.
The biggest concern is herpes viruses, including the herpes simplex virus (HSV-1), which causes cold sores – and is transmitted by four in five adults.
It is estimated that up to 95 percent are also carriers of the varicella-zoster virus, another type of herpes virus that causes chickenpox and shingles.
The scientists from Britain and the US hope that the promising findings – carried out in laboratory settings and not on humans – can help speed up research into antiviral drugs for herpes that can slow the onset of degenerative diseases.
Professor Ruth Itzhaki, visiting researcher at the University of Oxford’s Institute of Population Aging, said: ‘What we have found is that these injuries in the brain model can reactivate a dormant virus, HSV-1.
‘This causes inflammation in the brain that would lead to exactly the changes we see in Alzheimer’s patients.’
Scientists believe head injury can ‘wake up’ dormant herpes viruses in the brain, causing inflammation and longer-term damage
Studies have long warned that concussions and blows to the head can increase the risk of neurodegenerative diseases. Former rugby player Steve Thompson was diagnosed with early-onset dementia at the age of 43
Dr. Dana Cairns, a research fellow in biomedical engineering at Tufts University in Boston, added: ‘This opens up the question of whether antiviral drugs or anti-inflammatory drugs could be useful as early preventative treatments after head trauma to stop the activation of HSV-1 in his head. follow and reduce the risk of Alzheimer’s disease.’
In the study, researchers recreated a model brain in the laboratory, placing it in a cylinder to mimic the skull.
Some brain cells were infected with the dormant herpes simplex virus (HSV-1), which causes cold sores.
They then gave the mini-brains a single hard blow with a piston to mimic a traumatic head injury, or a series of smaller shocks to mimic the effects of a periodic milder concussion.
When the brain tissues were exposed to repeated ‘mild blows’, the previously dormant HSV-1 virus became active.
This reactivation caused inflammation, the buildup of beta-amyloid plaques and the formation of harmful tau proteins, hallmark markers of Alzheimer’s disease.
There was also evidence of reduced function of brain cells.
With further attacks on brain tissue, which mimicked repeated head injuries, the damage was more severe – but brain cells without herpes infection did not show the same problems as a result of the blows.
Alzheimer’s disease is the most common cause of dementia. The disease can cause anxiety, confusion and short-term memory loss
Writing in the diary Scientific progressthe scientists said: ‘We suggest that after brain injury from repeated mechanical blows in life, the resulting HSV-1 reactivation in the brain leads to the development of Alzheimer’s disease/dementia.
‘(This suggests) that HSV-1 is a major cause of Alzheimer’s disease.’
However, other scientists not involved in the study have urged caution about the findings.
Professor Robert Howard, Professor of Old Age Psychiatry at University College London, said: ‘The study is interesting and suggests a potential mechanism for the observed link between cold sore virus infection, brain damage and Alzheimer’s disease.
‘But as is often the case in science, it is very important to keep in mind that association does not equal causation.
‘Much more research will be needed before this can be seriously considered as a plausible mechanism for the development of dementia.
‘Avoiding brain injury, such as that seen in some contact sports, is already known as an important way to prevent dementia and I am not convinced that this reflects anything more complicated than mechanical damage that causes brain cell death.’
Research has suggested that multiple blows to the head can more than double the risk of a neurodegenerative condition months or years later.
Sir Bobby Charlton (pictured holding a ball with United written on it during an interview with the local press at a Hong Kong hotel in 2005) died aged 86 from dementia in 2023
Former England and West Bromwich Albion striker Jeff Astle died aged 59 from an early illness – reportedly due to repetitive head trauma
Contact sports have been marred in controversy due to links to dementia and other brain diseases in players, which are believed to result from frequent impacts to the head.
Most famously, former England footballer Sir Bobby Charlton died in 2023 at the age of 86, years after being diagnosed with dementia.
Former England and West Bromwich Albion striker Jeff Astle died aged 59 from an early illness – reportedly due to repetitive head trauma.
Former rugby player Steve Thompson was also diagnosed with early-onset dementia at the age of 43.
A 2023 study commissioned by the Football Association and Professional Footballers’ Association found that professional footballers are three times more likely to be diagnosed with dementia than the general population.
But research published last year by scientists at the University of New South Wales in Australia found that those who had suffered a concussion while playing sports during their lifetime had marginally better cognitive performance than those who did not report a concussion.
Recent analysis by the Alzheimer’s Society estimates that the total annual cost of dementia to Britain is £42 billion per year, with families bearing the brunt.
An aging population means these costs – including the lost income of unpaid caregivers – are expected to rise to £90 billion over the next fifteen years.
Around 900,000 Britons are currently thought to suffer from memory theft disorder. But scientists at University College London estimate that this number will rise to 1.7 million within 20 years as people live longer. It represents an increase of 40 percent compared to the previous forecast in 2017
It is thought that around 944,000 people in Britain are living with dementia, while in the US the figure is around 7 million.
Alzheimer’s disease affects about six in ten people with dementia.
Memory problems, thinking and reasoning problems, and language problems are common early symptoms of the condition, which then worsen over time.
Dementia is expected to explode in the coming years, making a low-cost screening tool crucial to meet the challenge.
The analysis by Alzheimer’s Research UK found that 74,261 people died from dementia in 2022, up from 69,178 a year earlier, making it the country’s biggest killer.