New study shows risk factors for dementia – virus causes deposits in the brain

Research into the causes of Alzheimer's is not yet complete. Now a new study shows that head trauma can activate herpes viruses and promote the disease.

Frankfurt am Main – As a neurodegenerative disease, dementia often causes a lot of suffering for those affected and their relatives. While short-term memory and memory are initially impaired, dementia often progresses in such a way that it also deprives those affected of content imprinted in their long-term memory. In the course of the disease, those affected lose more and more of what they have learned, until in the course of a severe course of dementia there can even be a complete loss of perception. This is often accompanied by an increased level of care and need for care of those affected.

As an umbrella term, dementia includes around 50 clinical pictures that are associated with a reduction in memory and mental performance. Its most common form is Alzheimer's disease, which accounts for around two-thirds of all dementia cases. Although exercise, a balanced diet and mental training can prevent it, there are also a number of risk factors that can promote Alzheimer's. And a recently published British study now suggests a surprising connection for these.

Study shows connection between herpes viruses and head injuries as risk factors for Alzheimer's dementia

The development of Alzheimer's dementia is an important question in research and as such the subject of numerous dementia research studies, but its causes are still not fully understood. One thing is clear: In those affected, nerve cells in the brain deteriorate, which further impair their mental performance and perception over the course of the disease.

At present, Alzheimer's research assumes that deposits of two toxic proteins are largely responsible for the breakdown of nerve cells in those affected: clumps of amyloid-beta and tau fibrils. However, herpes viruses and head injuries, such as concussions in particular, also seem to have a risk of promoting the development of Alzheimer's dementia under certain circumstances.

Head injuries "awaken" herpes viruses – and release proteins that promote Alzheimer's disease

At least this is the central finding of a British study that researchers from the Institute for Population Ageing at the University of Oxford worked out together with members of the Universities of Manchester and Tufts. They published their results in the journal Science Signaling. As the researchers discovered, herpes viruses can survive a lifetime in the human body and lead to the dreaded deposits in the brain if they are "awakened", i.e. reactivated, in a certain way.

Herpes viruses that lie dormant in the body for a long time could be "awakened" by vibrations and injuries to the head, for example, as the scientists pointed out as the next important result of their study in Science Signaling. They reached it by exposing a biotechnologically generated model of human brain tissue to a series of light shocks.

They observed how light shocks activated the dormant herpes viruses. "This reactivation triggered inflammation, the formation of beta-amyloid plaques and the formation of harmful tau proteins," summarized Leslie K. Ferrarelli, who was involved in the study as a researcher. And because these proteins are known to initiate neurodegenerative processes in the brain, including Alzheimer's dementia, Ferarelli adds: "The results establish a direct link between two risk factors in a mechanism that may contribute to dementia."

Head injuries have long been known to science as a risk factor for dementia

While the researchers have now made an important new finding with the connection between head injuries and a reactivation of herpes viruses as the cause of Alzheimer's dementia, effects on the skull have long been identified as a risk factor for dementia. Chronic traumatic encephalopathy (CTE) even exists as a clinical picture that classifies a rare form of dementia: cognitive and motor disorders as well as behavioral and personality changes that occur as a result of regular head injuries.

It was first described by US researchers in the 1920s as "punch drunk syndrome". The reason for the study at that time was a sometimes noticeable limitation of the cognitive performance of professional boxers, who are known to be exposed to a high number of blows to the head during training or competitions.

Because contact sports in particular, and thus numerous team sports such as football or basketball in addition to those from martial arts, offer an increased potential for head injuries, the Alzheimer Research Initiative e.V. association warns on its website to protect the head during sports and to avoid unnecessary vibrations – even minor ones. And not only because there is no therapy for CTE sufferers yet, but because head injuries can also promote Alzheimer's dementia. For this reason, older people are also recommended to exercise increased caution against falls. (FH)