Alzheimer’s disease could be triggered by common virus – as scientists warn it could travel from the gut to the brain
ALZHEIMER’S could be triggered by a common bug that travels from the gut to the brain, researchers believe.
US scientists found telltale signs of a specific herpes virus in the brains of people who’d died with the brain-eating disease.
The virus, called cytomegalovirus (HCMV), is one of nine herpes viruses – but not the type linked to cold sores or sexually transmitted infections.
It spreads through bodily fluids like saliva, and most people catch it during childhood without any symptoms.
The bug was present in up to half of cases of the disease studied.
Researchers from Arizona State University think that in some people, this virus could stick around, stay active and hitch a ride to the brain along the vagus nerve – the body’s superhighway between the gut and brain.
Once it gets there, it seems to set off immune reactions that could help form the sticky plaques and tangles that stop brain cells from communicating properly with each other.
Study author, Dr Ben Readhead, a neurodegenerative disease expert, said: “We think we found a biologically unique subtype of Alzheimer’s that may affect 25 to 45 per cent of people with this disease.”
Alzheimer’s is the most common form of dementia, the UK’s biggest killer.
It’s a brain disorder that gradually destroys memory and thinking skills, and eventually, the ability to perform everyday tasks.
This form of Alzheimer’s looked at in this study involves the usual brain changes like amyloid plaques and tau tangles.
But it also comes with a distinct viral footprint, plus antibodies and immune cells that stir up inflammation.
Post-mortem exams showed Alzheimer’s patients had more immune cells driving inflammation, while their guts and spinal fluid showed clear signs of viral activity.
The team also found traces of the virus in the vagus nerve, hinting at how it travels to the brain.
The virus usually spreads through bodily fluids but stays dormant in most healthy people.
By age 80, around 80 per cent of us have antibodies to it, but the researchers spotted active infections in people with Alzheimer’s, suggesting a link.
Now, the team is working on a blood test to spot this chronic gut infection early.
They think it could be treated antivirals and potentially prevent Alzheimer’s from taking hold.
Ways to lower your risk of dementia
There are things you can do to reduce your own risk of developing dementia, including Alzheimer's.
No single behaviour is guaranteed to prevent dementia – but there’s lots of evidence to suggest that making tweaks to your lifestyle choices could affect your risk.
Dementia risk is lowest in people who have healthy behaviours in mid-life – from the age of 40 to 65 – according Alzheimer’s Society.
Here are a few easy changes you can make:
- Exercise regularly to boost your heart health and circulation and help maintain a healthy weight.
- Drink less alcohol – try to have no more than 14 units of alcohol a week, about one pint of beer or a small glass of wine each day. If you regularly drink much more than this, you are increasing your risk of damage to your brain and other organs, and so increasing your risk of dementia.
- Don’t smoke – it does a lot of harm to the circulation of blood around the body, particularly the blood vessels in the brain, as well as the heart and lungs.
- Engaging in social activities to help to build up your brain’s ability to relieve stress and improve your mood – depression and social isolation have both been linked to dementia.
- Manage health conditions, such as high blood pressure, high cholesterol or diabetes, which can increase the risk of getting dementia.
- Protect your eyesight and hearing – vision loss increases a person’s risk of developing dementia. The same goes for hearing loss, which can also be an early symptom of dementia.
- Wear a helmet – as traumatic brain injuries can start a process in the brain where the substances that cause Alzheimer’s disease build up around the injured area.
Source: Alzheimer’s Society
Dr Eric Reiman, the study’s senior author, said: “We’re thrilled at the possibility of our findings shaping the study, treatment, and prevention of Alzheimer’s.”
The team’s findings, published in Alzheimer’s & Dementia, could lead to big changes in how the disease is treated.
If confirmed, existing antiviral drugs might help treat or prevent this form of Alzheimer’s.
Researchers are even developing a blood test to identify people with an active HCMV infection who could benefit from treatment.
The discovery opens the door to new possibilities for tackling Alzheimer’s.
While more studies are needed, it highlights how common infections like HCMV could play a hidden role in brain health – and what we might do to stop it.