2023-06-20 08:49:26
Around 1.8 million people in Germany live with dementia, and the number is expected to rise to 2.8 million by 2050. The details of the disease are well described: those affected lose their memory, are confused and can no longer live independently.
The most common type of dementia is Alzheimer’s disease. The cells in the brain produce deposits that “glue” the tissue. As a result, more and more nerve cells die and the brain functions less and less well.
Emanuel Wyler conducts research at the Max Delbrück Center for Molecular Medicine in Berlin. His main research areas include herpes and corona viruses, including within the framework of the research project funded by the German Research Foundation Projekts DEEP-DV
But the big mystery is still what actually triggers these destructive processes. Infections with bacteria or viruses have long been suspected, but the evidence so far is rather thin.
Herpes viruses: professionals in hiding
Thanks to a historically unique starting position, a new study now brings a new clue: Varicella-zoster viruses, the causative agent of chickenpox, may contribute to the development of dementia. It would be further evidence that viruses can cause long-term health damage that we are far from understanding.
Most viruses that we encounter in Germany make you sick to a greater or lesser extent immediately after infection. This is followed by a phase of recovery, which sometimes lasts months to years, but often only a few days. In most cases, the virus is gone from the body after a few days to a few weeks.
2,8
millions There will probably be dementia patients in Germany alone in 2050
The group of herpes viruses behaves completely differently. You get infected with most of them in the first few years of life, after which they “hide” in the body for the rest of your life. Some of the nine herpesviruses that infect humans are found in almost all of the world’s population; and the problem is: Sometimes, and only years or decades after infection, they can cause serious illnesses.
Painful and uncomfortable
The most well-known herpes virus is herpes simplex, which triggers the painful and unpleasant “fever blisters” or “cold sores”. About seven to nine out of ten people carry this virus – in a dormant, “latent” form, in the facial nerves. In some people, the virus reactivates at some point, such as when they are stressed or infected with bacteria or other viruses. It then migrates into the skin cells of the lips, where it multiplies very quickly, resulting in the cold sore.
In rare cases (a few hundred per year in Germany) such a reactivation takes place in the brain. Life-threatening encephalitis occurs. Even with rapid antiviral treatment, many of those affected suffer for life, for example from epileptic seizures.
So far, the paths of the virus are still understandable. Herpes simplex has been around for a long time but also suspectto contribute to the development of Alzheimer’s disease. The virus was found in the brains of deceased people in the areas where Alzheimer’s damage begins.
According to this, the virus could migrate from the facial nerves in the wrong direction and arrive in the brain – but then not cause a large-scale infection with noticeable encephalitis, but only small-scale damage, which in turn would then be the trigger for the deposits mentioned at the beginning.
However, solid evidence for this thesis is lacking. This is also because many decades elapse between contracting the virus (in infancy) and the onset of the disease, and there is a connection therefore difficult to produce.
Unique opportunity
In addition to herpes simplex, other herpesviruses are also being investigated for a possible contribution to Alzheimer’s or, more generally, to dementia. A close relative of herpes simplex is the varicella-zoster virus, which causes chickenpox in children and shingles in adults.
In order to reduce reactivations in old age and thus shingles, there has been a vaccination against the varicella zoster virus for a good ten years – and the introduction of this vaccination has a unique opportunity imperative to study the relationship between virus and dementia.
Because in Wales, part of Great Britain, the vaccination was introduced in 2013 – but only for everyone under 80. This means that all people born before September 2nd, 1933 were not vaccinated, everyone after that was.
The most common type of dementia is Alzheimer’s disease. Deposits stick together the fabric; as a result, more and more nerve cells die off. © mauritius images / Science Photo Library
There were thus two comparable groups, with and without varicella zoster vaccination, to examine whether the vaccination has an impact on new cases of dementia. And that was indeed the case: the vaccination reduced the incidence of this by 20 percent, taking into account the different ages of the two groups. The effect was significantly greater in women than in men.
The incidence of shingles decreased to a similar extent. Since everyone carries the virus, vaccination seems to “only” prevent reactivation. The explanation for the observation could be that because of the vaccination, the varicella-zoster virus reactivates less often and can therefore contribute less to the development of dementia.
Better vaccine available
Even if this sounds conclusive at first, the data should still be treated with caution. Because the cut-off date compares groups of different ages, and the older the people, the more common dementia occurs. Even if this effect was eliminated in the study, it is not yet possible to conclusively assess the contribution of the virus to the development of dementia – and the fact that the vaccination primarily protects women from dementia poses the next puzzle.
Assuming that the virus is really an important factor in the development of dementia: then, in many decades, one will perhaps also see an influence of the vaccination against varicella zoster in early childhood, which started in Germany in 2006, and relatively quickly has led to significantly less chickenpox. If this vaccination could ensure that the virus does not even take root in the body, it cannot cause dementia decades later.
More about dementia
How Alzheimer’s begins Towards early detection of dementia Disoriented, confused, hallucinating Does delirium cause dementia? Alzheimer’s Finally a glimmer of hope
A significantly better vaccine has been available for adults since 2018; in the future it will be interesting to investigate whether this can also have an effect on the frequency of dementia.
Herpesviruses are our lifelong companions. It is difficult to test whether and to what extent they actually cause dementia diseases such as Alzheimer’s; favorable opportunities such as vaccination rules in Wales are rare. In any case, they are an example of how annoying viruses can be even without a pandemic.
1687251894
#British #study #shingles #vaccination #clues