New research shows that Herpes infections may increase the risk of Alzheimer’s disease. In addition, antiviral drugs may reduce the risk of senile dementia in patients with severe herpes infections.
Herpes viruses remain lifelong in neurons and immune cells, reactivating and resurfacing in blisters when a person is rundown by stress or illness. The majority of people are infected by the Herpes Simplex Virus 1 (HSV1), the cause of cold sores, by the time they reach old age.
“HSV1 could account for 50 percent or more of Alzheimer’s disease cases,” professor Ruth Itzhaki, who has spent over 25 years at the University of Manchester investigating a potential link, said in a statement.
Itzhaki previously found that cold sores occur more frequently in those who carry a gene variant that confers increased risk of Alzheimer’s called APOE-ε4.
“Our theory is that in APOE-ε4 carriers, reactivation is more frequent or more harmful in HSV1-infected brain cells, which as a result accumulate damage that culminates in development of Alzheimer’s,” she said.
While very few countries collect the population data needed to test Itzhaki’s theory, Taiwanese researchers enrolled 99.9 percent of the country’s population in a National Health Insurance Research Database that is being mined for information on microbial infections and disease.
Three studies were published between 2017 and 2018 describing Taiwanese data on the development of senile dementia–which is mainly caused by Alzheimer’s–and the treatment of patients with marked overt signs of infection with HSV or varicella zoster virus (VZV), commonly known as chickenpox.
“The striking results include evidence that the risk of senile dementia is much greater in those who are infected with HSV, and that anti-herpes antiviral treatment causes a dramatic decrease in number of those subjects severely affected by HSV1 who later develop dementia,” Itzhaki said.
The data from Taiwan only applies to the rare severe HSV1 or VZV infections.
The next step will be to study dementia rates amongst people with mild HSV1 infections, including herpes labialis or mild genital herpes.
“Considering that over 150 publications strongly support an HSV1 role in Alzheimer’s, these Taiwan findings greatly justify usage of antiherpes antivirals – which are safe and well-tolerated – to treat Alzheimer’s disease,” Itzhaki said.”They also incentivize development of an HSV1 vaccine, which would likely be the most effective treatment.”
The study was published in Frontiers in Aging Neuroscience.