Catching shingles may increase the risk of Alzheimer’s, scientists say.
A study led by the University of Oxford found that infection can trigger a dementia-related chain reaction in the brain.
It does this by awakening another normally harmless herpes virus that has been dormant in our bodies since childhood.
This leads to the formation of a “dramatic” plaque and inflammation in the brain, the two hallmarks of Alzheimer’s disease.
Chickenpox occurs when the body is first exposed to the varicella zoster virus (VZV), usually as a child. Shingles is caused by later infections.
To see the effect of VZV on the brain, the researchers used lab-grown brain cells to create a three-dimensional brain.
They found that it did not directly cause the characteristic changes associated with Alzheimer’s disease.
But it reactivated the simplex virus (HSV-1), best known for causing herpes, causing a rapid buildup of harmful proteins.
“These are two viruses that are common and mostly harmless,” said study author Dana Cairns, of Tufts University in Massachusetts.
Catching shingles can trigger a chain reaction in the brain, increasing the risk of Alzheimer’s, scientists warn (file image)
“However, laboratory studies show that reexposure to VZV can cause problems if it awakens dormant HSV-1.”
Normal HSV-1 the body is dormant, and there is strong evidence that it may be linked to dementia.
Previous research has found that older people with high levels of the virus in their brains have a much higher risk of Alzheimer’s disease.
University of Manchester Professor Ruth Itzhaki collaborated on the latest study with researchers from the Oxford Institute on Population Aging and Tufts University.
The researchers created brain-like environments in ring-shaped 6mm wide sponges made of silk proteins and collagen.
They filled the sponges with stem cells that turn into neurons and can transmit signals to each other, just like in the brain.
The results showed that neurons in the brain can be infected with VZV, but this alone does not lead to plaque formation and cell death.
Virus-infected neurons can still function normally.
However, if the cells also harbored HSV-1, there was a dramatic increase in tau and beta-amyloid proteins, which are strongly associated with dementia.
Neuronal signals also began to slow down.
Professor Itzhaki said: “This surprising result seems to confirm that infections such as VZV can cause increased inflammation in the brain in humans, which can reactivate dormant HSV-1.
‘Brain damage from repeated infections throughout life will eventually lead to the development of AD/dementia.
“This means that vaccines may play a larger role than protecting against a single disease, as they may indirectly provide some protection against Alzheimer’s disease by reducing infections.”
The study was published in the Journal of Alzheimer’s Disease.
Shingles can be very painful and tends to affect people more often as they get older.
About one in five people who get chickenpox develops shingles, and most are 70 years old.
Researchers also warn that obesity, smoking, alcohol and head injuries can also increase the risk of Alzheimer’s by weakening the immune system and activating dormant HSV1 in the brain.
More than 900,000 people live with dementia in the UK today, and that number is expected to rise to 1.6 million by 2040.
Alzheimer’s disease is the most common form of dementia.
Current estimates are that approximately 5.8 million people in the United States have the condition, most of whom are over the age of 65.
Source: Daily Mail
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