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Shingles may raise your risk of Alzheimer’s: Infection is linked to dramatic plaque build-up in brain, study finds
- Study led by Oxford University found shingles infection ‘sets off chain reaction’
- Wakes up different, normally-harmless herpes virus that lays dormant in body
- This leads to a ‘dramatic’ accumulation of plaque and inflammation in the brain
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Catching shingles may raise the risk of Alzheimer’s disease, scientists have warned.
A study led by Oxford University found the infection can set off a chain reaction in the brain linked to dementia.
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.
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.