2024-02-20 17:10:00
Study examines connection herpes viruses can double the risk of Alzheimer’s
By Hedviga Nyarsik February 20, 2024, 6:10 p.m. Listen to article
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If your lip tingles and itches, it can usually only mean one thing: herpes. Once you have been infected with the virus, it remains in the body for life and causes unpleasant blisters for some people. However, these are only the visible consequences. According to a study, herpes viruses can significantly increase the risk of Alzheimer’s.
First the lip tingles and itches, then it swells and finally small blisters form: people with cold sores know these symptoms all too well. The trigger is the herpes simplex virus type 1 (HSV-1). According to estimates by the Federal Health Office, 60 to 90 percent of people carry this type of virus, often unnoticed. The pathogen can not only cause unpleasant symptoms, but also significantly increase the risk of Alzheimer’s, as a new study has found.
The herpes virus is treacherous. Once you have become infected, the viruses nest in the nerve cells and remain there for life. Often there are no symptoms at all and the herpes viruses lie dormant in the body in a so-called state of latency. Only when the immune system is weakened by a severe infection or stress do symptoms such as the typical blisters appear.
However, these are only the visible signs that HSV-1 causes. It has long been suspected that they could also be involved in the development of Alzheimer’s disease. To examine this connection in more detail, Swedish researchers observed more than a thousand 70-year-olds over a period of 15 years in a long-term study published in the Journal of Alzheimer’s Disease.
The result: Of the 1,002 participants, 82 percent were carriers of HSV-1 antibodies. This means that their immune system was exposed to the pathogen at some point in the past. The authors write that these patients were twice as likely to develop dementia during the course of the study as those who did not have HSV-1 antibodies.
A risk factor for dementia?
“The special thing about this study is that the participants are approximately the same age, as age differences, which are otherwise associated with the development of dementia, cannot confound the results,” says epidemiologist Erika Vestin from Uppsala University in Sweden. This makes the results even more reliable. They also confirmed previous studies. “There is increasing evidence from studies that, like our results, suggest that the herpes simplex virus is a risk factor for dementia,” said the co-author.
Alzheimer’s dementia
Alzheimer’s dementia (AD) is a disease that has been described for more than 100 years, but despite great efforts, the actual cause is still not known. It accounts for two thirds of all dementia cases. It is currently assumed that more than 50 million people are affected worldwide. Projections paint a dramatic scenario with 106 to 360 million cases in 2050.
This neurodegenerative disease begins gradually between the ages of 45 and 50. The clinical symptoms only become apparent in everyday life 20 to 30 years later. It can start with standing in a department store and suddenly not being able to find your way out or leaving your purchase at the checkout. Even minor memory impairments that occur for the first time can be harbingers of this disease.
The Swedish study does not provide evidence that HSV-1 actually causes dementia. According to the researchers, further investigations are necessary. Nevertheless, it shows a strong connection between a herpes infection and the occurrence of Alzheimer’s. The results “could advance dementia research toward early treatment of the disease with common anti-herpes virus drugs or prevent the disease before it occurs,” Vestin hopes.
What exactly causes Alzheimer’s remains a mystery in medicine to this day. The biggest risk factor is age. Most of those affected are older than 80 years, and only in rare cases does the disease begin before the age of 65. It leads to a breakdown of nerve cells in the brain. Protein deposits between the nerve cells, called plaques, are characteristic. They consist of an amyloid core that is surrounded by modified nerve cell processes and supporting cells – and lead to increasing destruction of the brain’s nerve cells.
There is no safe protection
The idea that infections could trigger some variants of Alzheimer’s disease is not new: in the 1990s, unusual amounts of HSV-1 DNA were first found in the brains of deceased Alzheimer’s patients. In 2008, researchers discovered that HSV-1 DNA was present in 90 percent of the protein plaques in postmortem brains of Alzheimer’s patients. What’s more: 72 percent of the HSV-1 DNA in the brain was within these plaques. The results suggest that the immune response to the herpes virus is closely linked to cognitive decline.
There is currently no vaccine against HSV-1. At the same time, the virus is very easily transmittable. There is a particularly high risk of direct contact with the blisters or ulcers, for example when kissing or having sex. Herpes viruses can also be passed on through droplet and smear infections, for example through coughing, sneezing or sharing glasses or cutlery.
Because herpes is so easily transmitted, there is no reliable protection. It is important to avoid contact with cold sores and herpes ulcers – including your own, so as not to transmit viruses from your lips to your eyes. If you have touched the blisters, washing your hands thoroughly will help.
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