A ‘harmless’ virus carried by half of all adults could raise the risk of Alzheimer’s, shock research suggested today.
Cytomegalovirus (CMV), which causes a cold-like illness, can be spread in the same way as other viruses from person to person through body fluids such as blood, saliva and urine.
But the infection is present in up to 45 per cent of Alzheimer’s cases, US scientists have claimed.
Some people exposed to the bug may develop a chronic intestinal infection, allowing it to enter the bloodstream and travel to the brain.
Here, it is recognised by the brain’s immune cells — microglia — the researchers say, helping to contribute to the biological changes involved in Alzheimer’s.
The scientists, who labelled the findings ‘exciting’, hope the research could pave the way to confirming whether common antiviral drugs used to treat CVM may help prevent this form of the memory-robbing illness.
They cautioned, however, that simply coming into contact with the virus — which happens to almost everyone — should not be cause for concern.
The infection only appears to be associated with Alzheimer’s when it is found in the brain.
NICE also said it had identified 27 other drugs which it ‘expects to be asked to evaluate over the next few years’
Alzheimer’s disease is the most common cause of dementia. The disease can cause anxiety, confusion and short-term memory loss
To date, no single illness yet has also consistently been linked to the disease.
Dr Ben Readhead, study co-author and associate professor in neurodegenerative diseases at Arizona State University, said: ‘We think we found a biologically unique subtype of Alzheimer’s that may affect 25 per cent to 45 per cent of people with this disease.’
This subtype, he added, features a build-up of the proteins amyloid and tau in the brain — a hallmark of Alzheimer’s — as well as a ‘distinct profile of [the CVM] virus, antibodies and immune cells in the brain’.
‘This subtype of Alzheimer’s includes the hallmark amyloid plaques and tau tangles—microscopic brain abnormalities used for diagnosis—and features a distinct biological profile of virus, antibodies and immune cells in the brain.’
In the study, the scientists examined spinal fluid to track how CVM antibodies move in the body.
They found CMV within the vagus nerve, which carries signals between the brain, heart and digestive system, and suggested this was how the virus travels to the brain.
Tests on human brain cells then showed the virus increased the production of amyloid and tau proteins and contributed to the degeneration and death of neurons.
Writing in the journal Alzheimer’s and Dementia, the researchers said the study illustrates the impact that infections can have on brain health and neurodegeneration broadly.
Around 900,000 Brits are currently thought to have the memory-robbing disorder. But University College London scientists estimate this will rise to 1.7million within two decades as people live longer. It marks a 40 per cent uptick on the previous forecast in 2017
But further independent studies are needed to put their findings and resulting hypotheses to the test, they added.
Dr Eric Reiman, executive director of Banner Alzheimer’s Institute and study senior author, also said: ‘We’re excited about the chance to have researchers test our findings in ways that make a difference in the study, subtyping, treatment and prevention of Alzheimer’s disease.’
Recent analysis by the Alzheimer’s Society estimates the overall annual cost of the dementia to the UK is £42billion a year, with families bearing the brunt.
An ageing population means these costs – which include lost earnings of unpaid carers – are set to soar to £90billion in the next 15 years.
Around 944,000 in the UK are thought to be living with dementia, while the figure is thought to be around 7million in the US.
Alzheimer’s affects around six in 10 people with dementia.
It is thought to be caused by a build-up of amyloid and tau in the brain, which clump together and from plaques and tangles that make it harder for the brain to work properly.
Eventually, the brain struggles to cope with this damage and dementia symptoms develop.
Memory problems, thinking and reasoning difficulties and language problems are common early symptoms of the condition, which then worsen over time.
Dementia are expected to sky-rocket in the coming years, making a cheap screening tool vital to get to grips with the challenge.
Alzheimer’s Research UK analysis found 74,261 people died from dementia in 2022 compared with 69,178 a year earlier, making it the country’s biggest killer.