Scientists have warned that having shingles may increase the risk of Alzheimer’s disease.
An Oxford University study found that infection can trigger a chain reaction in the brain linked to dementia.
It does this by awakening a different, usually harmless, herpes virus that has been dormant in our bodies since childhood.
This leads to a “dramatic” buildup of plaques and inflammation in the brain – two hallmarks of Alzheimer’s disease.
Chickenpox occurs when the body is first exposed to the varicella zoster virus (VZV), usually in children. Shingles is the result of a subsequent infection.
The researchers used lab-grown brain cells to create a 3-D brain to see the effect of VZV on the brain.
They found that it does not directly lead to the signature changes associated with Alzheimer’s disease.
But it reactivated HSV-1, which is better known for causing cold sores, resulting in a rapid buildup of harmful proteins.
‘It’s one or two punches from two very common and usually harmless viruses,’ said study author Dana Kearns, of Tufts University in Massachusetts.
Scientists have warned that catching shingles may increase the risk of Alzheimer’s disease by triggering a chain reaction in the brain (file photo)
But lab studies suggest that if new exposure to VZV activates dormant HSV-1, it can cause problems.
HSV-1 naturally Latent in the body and there is strong evidence that it could be linked to dementia.
Previous research has suggested that older adults who have high levels of the virus in their brain are at greater risk of developing Alzheimer’s disease.
Professor Ruth Itzaki, from the University of Manchester, worked with researchers from the Oxford Institute on Population Aging and Tufts University on the latest study.
The researchers recreated brain-like environments in a 6-millimeter-wide doughnut-shaped sponge made of silk protein and collagen.
They filled the sponge with stem cells that grew into neurons and were able to pass signals to each other, just as they would in the brain.
The results showed that neurons in the brain can be infected with VZV, but that this alone does not lead to plaque formation and cell death.
The virus-infected neurons were still able to function normally.
However, if cells harbor HSV-1 as well, there will be a significant increase in tau and beta-amyloid proteins, which are strongly associated with dementia.
The nerve signals also began to slow down.
Professor Itzaki said: ‘This astonishing 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.
Damage to the brain from repeated infections over a lifetime will eventually lead to Alzheimer’s disease/dementia.
This means that vaccines can play a greater role than just protecting against a single disease, because they can also indirectly, by reducing infection, provide some protection against Alzheimer’s disease.
The study was published in the Journal of Alzheimer’s Disease.
Shingles can be very painful and tend to affect people more commonly as they age.
About one in five people who have chickenpox develop shingles, most of them in their 70s.
The researchers also warn that obesity, smoking, alcohol, and head trauma may also increase the risk of Alzheimer’s disease 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, and this is expected to rise to 1.6 million by 2040
Alzheimer’s disease is the most common type of dementia.
Current estimates are that about 5.8 million people in the United States have this disorder, most of them over the age of 65.