Scientists have warned that harboring tumors may increase the risk of Alzheimer’s disease.
A study by the University of Oxford found that the infection could trigger a chain reaction in the brain linked to dementia.
It does this by awakening another, usually harmless, herpes virus that has been dormant in our bodies since childhood.
This leads to a “dramatic” buildup of plaque and inflammation in the brain, two hallmarks of Alzheimer’s.
Chickenpox occurs when the body is first exposed to the varicella zoster virus (VZV), usually during childhood. Shingles is the result of subsequent infections.
To see how VZV affects the brain, the researchers used lab-grown brain cells to create three-dimensional brains.
They found that Alzheimer’s disease did not directly cause signature changes.
But it reactivated the herpes simplex virus (HSV-1), which is known to cause cold sores, prompting rapid accumulation of harmful proteins.
Study author Dana Cairns, from Tufts University in Massachusetts, said: “It’s a one-two punch of two very common and usually harmless viruses.
Tumors increase risk of Alzheimer’s disease, scientists warn, triggering chain reaction in brain (file photo)
“But laboratory studies show that new exposure to VZV can cause problems if HSV-1 wakes up from sleep.”
HSV-1 usually sleep in the body and there is strong evidence that it is linked to dementia.
Previous research has shown that older adults with higher levels of the virus in their brains are at a higher risk of developing Alzheimer’s disease.
Professor Ruth Yitzhaky of the University of Manchester worked with researchers from Oxford’s Institute of Population Aging and Tufts University on the latest study.
The researchers recreated brain-like environments in 6-millimeter donut-shaped sponges made of silk protein and collagen.
The sponges were filled with stem cells that became neurons and could 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.
The infected neurons were still able to function normally.
However, if the cells also contained HSV-1, there was a dramatic increase in tau and beta-amyloid proteins, which are closely related to dementia.
Neuronal signals also began to slow down.
Professor Itzaki said: ‘This surprising finding suggests that in humans, infections such as VZV can lead to increased inflammation in the brain, which reactivates dormant HSV-1.
“Brain damage from repeated infections over a lifetime eventually leads to the development of AD/dementia.
“These vaccines may play a role in more than just protection against the disease, because they may indirectly provide some protection against Alzheimer’s.”
The study was published in the Journal of Alzheimer’s Disease.
Shingles can be very painful and affects people more as they get older.
About one in five people who get chickenpox will develop chickenpox, and most of them are in their seventies.
Researchers also warn that obesity, smoking, alcohol and head trauma can increase the risk of Alzheimer’s disease by weakening the immune system and activating dormant HSV1 in the brain.
Today, more than 900,000 people in the UK are living with dementia, which is expected to rise to 1.6 million by 2040.
Alzheimer’s disease is the most common form of dementia.
Current estimates suggest that about 5.8 million people in the United States have the disease, most of whom are over 65 years of age.
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