Herpes may be behind half of Alzheimer's cases

But the study shows the link only applies to those who have had a severe HSV1 infection

As if it’s not bad enough that cold sores are unsightly and painful, they could cause up to 50% of cases of Alzheimer’s disease, according to a review.


But the good news is, according to lead author Professor Ruth Itzhaki from the University of Oxford, UK, that this makes antivirals are a justified treatment of Alzheimer’s.

The review of three studies published in the past two years that examined health insurance data from more than 99% of the Taiwanese population shows the risk of senile dementia is much greater in patients with severe cases of herpes simplex virus type 1 (HSV1) or varicella zosta virus (VZV) infection.

"HSV1 could account for 50% or more of Alzheimer's disease cases," says Professor Itzhaki, who has spent over 25 years at the University of Manchester investigating the potential link.

The study also shows that antiviral treatment leads to a dramatic decrease in the number of patients who later develop dementia.

However, the “striking” results only apply to patients with severe infection, which is rare, Professor Itshaki says.

But when considered alongside more than 150 studies that strongly support HSV1's role in Alzheimer’s, they “greatly justify” the use of antivirals to treat the disease, she writes.

"They also incentivise development of an HSV1 vaccine, which would likely be the most effective treatment," she says.

Professor Itzhaki has previously found that cold sores are more prevalent among people with a gene variant that also results in an increased risk of Alzheimer’s.

"Our theory is that in apolipoprotein-E 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 says. 

More information: Frontiers in Aging Neuroscience 2018