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Review shows link between herpes and dementia

Authors advocate use of antiherpes antivirals

Jo Carlowe

Friday, 19 October 2018

A research review, published today, suggests a role for herpes simplex virus type 1 in Alzheimer’s disease.

The paper* in Frontiers in Ageing Neuroscience states that people who have herpes simplex virus type 1 (HSV1) may be more likely to develop dementia. The authors say antiviral drugs may reduce dementia risk in such patients.

The evidence implies latent HSV1 in the brain of carriers of the type 4 allele of the apolipoprotein E gene (APOE-e4) is reactivated intermittently by events such as immunosuppression, peripheral infection, and inflammation, the consequent damage culminating in the development of Alzheimer’s disease (AD).

While population data to investigate this epidemiologically is not available in the UK, in Taiwan, the National Health Insurance Research Database (in which 99.9% of the population has been enrolled) has been extensively mined for information on microbial infections and disease. Three publications have now appeared describing data on the development of senile dementia (SD), and the treatment of those with marked overt signs of disease caused by varicella zoster virus (VZV), or by HSV. The striking results include evidence that the risk of SD is much greater in those who are HSV-seropositive, and that antiviral treatment causes a dramatic decrease in number of subjects who later develop SD.

“It should be stressed that these results apply only to those with presumed severe cases of HSV1 or VZV infection which are rare, but when considered with the over 130 publications that strongly support an HSV1 role in AD, they greatly justify usage of antiherpes antivirals to treat AD,” state the researchers.

Commenting on the findings, Dr James Pickett, head of research at Alzheimer’s Society, said: “Herpes is a hot topic in dementia research, as the infection appears to be more common in the brains of people with Alzheimer’s compared to healthy brains - but we don’t yet know enough about the relationship between the two.

“The link between herpes and dementia isn’t something that we feel people should worry about, although it’s sensible general advice to seek treatment for persistent cold sores. Dementia is not contagious and shouldn’t be thought of as an infectious disease.”

Dr Prickett added: “More research is needed to find out whether antiviral drugs can reduce dementia risk.”

*Itzhaki RF. Corroboration of a major role for herpes simplex virus type 1 in Alzheimer's disease. Front. Aging Neurosci. Doi: 10.3389/fnagi.2018.00324 

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