Half of Alzheimer's Diseases Due to Herpes Viruses?

Causes herpes to Alzheimer's?

Researchers have found a link between herpes viruses and Alzheimer's disease. Apparently, the herpes virus can be associated with at least half of all Alzheimer's cases. If people are infected with the herpes simplex virus (HSV), this may clearly increase the risk of dementia.

Researchers at the University of Manchester and the University of Oxford found in their current research that infection with herpes could increase the risk of dementia. The physicians published the results of their study in the English-language journal "Frontiers in Aging Neuroscience".

Herpes around the mouth and lips is caused by the herpes simplex virus type 1. This is apparently also related to Alzheimer's disease. (Image: Cherries / fotolia.com)

What types of herpes are there?

There are two types of herpes simplex viruses. HSV1, also known as oral herpes, causes cold sores and blisters around the mouth and face. HSV2 is generally responsible for genital herpes. The results of the study suggest that the risk of developing dementia in old age is much greater if those affected are infected with HSV. Antiviral treatment could lead to a drastic decrease in HSV1 cases, which in turn lead to dementia, according to study author Professor Ruth Itzhaki of the University of Manchester.

The evaluated data came from Taiwan

Data for the study came from Taiwan, with 99.9 percent of the population recorded in the National Health Insurance Research Database. In 2017 and 2018, a total of three studies were published using data from Taiwan to study the development of senile dementia. In addition, data were also considered for the treatment of patients with pronounced evidence of HSV or varicella-zoster virus (VZV) infection. It should be emphasized that the results of these studies were only for serious infections of HSV1 or VZV, explain the authors of the study.

APOE-? 4 gene plays an important role

Ideally, physicians would like to examine the rates of dementia in people who suffer from mild HSV1 infection, including herpes labialis (cold sores) or mild genital herpes, but such disorders are less documented. Herpes blisters are more common in people with APOE-? 4, a gene variant that increases the risk of Alzheimer's disease. Therefore, scientists suggest that in humans carrying the APOE-4 gene, reactivation in HSV1-infected brain cells is more frequent or more harmful, leading to damage culminating in the development of Alzheimer's disease. Viral DNA is very specific in plaques in the post-mortem brain tissue of Alzheimer's disease patients. The main proteins of so-called plaques and tangles also accumulate in HSV1-infected cell cultures and antiviral drugs can prevent this.

Further research is needed

The results of the study suggest that people with herpes virus infection are more likely to develop dementia, but they do not show a cause-and-effect relationship between herpes and dementia, say experts at the Alzheimer's Society. Herpes remains a hot topic in dementia research because brain infection is more common in people with Alzheimer's disease compared to healthy brains. Further research is now needed to find out if antiviral drugs can lower the risk of dementia. (As)