Catching shingles may raise the risk of Alzheimer’s disease, scientists have warned.
It does this by waking up a different, normally-harmless herpes virus that remains dormant in our bodies from childhood.
This leads to a ‘dramatic’ accumulation of plaque and inflammation in the brain — two hallmarks of Alzheimer’s.
Chickenpox happens when the body is first exposed to varicella zoster virus (VZV), usually as children. Shingles is the result of subsequent infections.
Researchers used lab-grown brain cells to create a three-dimensional brain to see what impact VZV has on the brain.
They found that it did not directly trigger the signature changes associated with Alzheimer’s.
But it did reactivate the simplex virus (HSV-1), better known for causing cold sores, triggering a rapid build-up of harmful proteins.
Study author Dana Cairns, from Tufts University in Massachusetts, said: ‘It’s a one-two punch of two viruses that are very common and usually harmless.
Catching shingles may raise the risk of Alzheimer’s disease by setting off a chain reaction in the brain, scientists have warned (file image)
‘But the lab studies suggest that if a new exposure to VZV wakes up dormant HSV-1, they could cause trouble.’
HSV-1 normally lies dormant in the body and there is strong evidence it could be linked to dementia.
Air pollution causes dementia, UK Govt admits for first time
Toxic airborne particles from cars and fossil fuels have long been associated with rapidly increasing rates of the disease in the UK and the developed world.
Now, a major independent review has confirmed the link after analysing dozens of human studies.
The researchers concluded it was ‘likely that air pollution can contribute to a decline in mental ability and dementia in older people’.
They believe the primary way this happens is by tiny toxic particles seeping into the bloodstream after being breathed into the lungs.
The pollutants then irritate blood vessels and disrupt circulation to the brain. Over time, this can lead to vascular dementia.
It is also likely that in rare cases very small air pollution particles can pass the blood-brain barrier and damage neurons directly.
But this does not seem to be an important mechanism at the level of air pollution currently in the UK, the report found.
Previous research has indicated elderly people with high levels of the virus in their brain are at a much higher risk of Alzheimer’s.
Professor Ruth Itzhaki, from the University of Manchester, worked with researchers from Oxford’s Institute of Population Ageing and Tufts University on the latest study.
Researchers re-created brain-like environments in 6 millimetre-wide donut-shaped sponges made of silk protein and collagen.
They populated the sponges with stem cells that grew into neurons and were capable of passing signals to each other, just as they do in the brain.
Results showed that neurons in the brain can be infected with VZV, but that alone does not lead to the formation of plaque and cell death.
Neurons that were infected with the virus were still able to function normally.
However, if the cells were also harbouring HSV-1 then there was a dramatic increase in tau and beta-amyloid proteins, strongly linked to dementia.
The neuronal signals also began to slow down.
Professor Itzhaki said: ‘This striking result appears to confirm that, in humans, infections such as VZV can cause an increase in inflammation in the brain, which can reactivate dormant HSV-1.
‘The damage in the brain by repeated infections over a lifetime would lead eventually to the development of AD/dementia.
‘This would mean vaccines could play a greater role than just protecting against a single disease, because they could also indirectly, by reducing infections, provide some protection against Alzheimer’s.’
The study was published in the Journal of Alzheimer’s Disease.
Shingles can be very painful and tends to affect people more commonly as they get older.
Around one in five people who have had chickenpox develop shingles, and most are in their seventies.
Researchers are also warning that obesity, smoking, alcohol and head trauma might also increase the risk of Alzheimer’s by weakening the immune system and activating dormant HSV1 in the brain.
More than 900,000 people are living with dementia in the UK today, which is projected to rise to 1.6million by 2040
Alzheimer’s disease is the most common type of dementia.
Current estimates are that about 5.8million people in the US have the disorder, with most being over the age of 65.
WHAT IS DEMENTIA? THE KILLER DISEASE THAT ROBS SUFFERERS OF THEIR MEMORIES
A GLOBAL CONCERN
Dementia is an umbrella term used to describe a range of progressive neurological disorders (those affecting the brain) which impact memory, thinking and behaviour.
There are many different types of dementia, of which Alzheimer’s disease is the most common.
Some people may have a combination of types of dementia.
Regardless of which type is diagnosed, each person will experience their dementia in their own unique way.
Dementia is a global concern but it is most often seen in wealthier countries, where people are likely to live into very old age.
HOW MANY PEOPLE ARE AFFECTED?
The Alzheimer’s Society reports there are more than 900,000 people living with dementia in the UK today. This is projected to rise to 1.6million by 2040.
Alzheimer’s disease is the most common type of dementia, affecting between 50 and 75 per cent of those diagnosed.
In the US, it’s estimated there are 6million Alzheimer’s sufferers. A similar percentage rise is expected in the coming years.
As a person’s age increases, so does the risk of them developing dementia.
Rates of diagnosis are improving but many people with dementia are thought to still be undiagnosed.
IS THERE A CURE?
Currently there is no cure for dementia.
But new drugs can slow down its progression and the earlier it is spotted the more effective treatments are.
Source: Alzheimer’s Society