Dementia risk ‘could be increased’ by common virus after scientists find link

New research indicates a link between a common type of herpes and Alzheimer’s disease.

Herpes is a common virus that can cause cold sores or genital sores and is spread through skin-to-skin contact. HSV-1 is most commonly associated with cold sores or oral herpes, while HSV-2 is usually linked to genital herpes.

Studies in the past have shown that HSV-1 can remain dormant within human cells, but can reactivate later in life and potentially trigger changes in the body like those seen in patients with dementia.

Alzheimer’s disease is the most common type of dementia. It involves cognitive decline caused by a build-up of abnormal proteins in the brain, which disrupts communication between nerve cells. This can interfere with daily life, affecting memory, language, problem-solving, and other thinking abilities.

The virus that causes cold sores may also be linked to Alzheimer's (Getty Stock Image)

A new large-scale study in the US involving researchers from pharmaceutical company Gilead Sciences and the University of Washington in Seattle has explored the connection between HSV-1 and the changes in the brain that are similar to those seen in Alzheimer's patients.

The research team analysed data from 344,628 individuals with Alzheimer’s and an equal number without the disease, all of whom were aged 50 or above. The team investigated the relationship between HSV-1 and Alzheimer's diagnoses between 2006 and 2021.

Individuals with a history of HSV-1 had an 80 percent higher risk of developing Alzheimer’s disease, even when other possible causes were considered.

Among participants with Alzheimer’s, 0.44 percent had a prior HSV-1 diagnosis, compared to 0.24 percent of those without the disease. The study population was approximately 65 percent women, with an average age of 73.

The virus responsible for cold sores may also be connected to Alzheimer's disease (Getty Stock Image)

Interestingly, the people who used antiviral medications to treat HSV-1 were 17 percent less likely to develop Alzheimer’s, suggesting managing the virus with antiviral medications could potentially lessen the risk of developing Alzheimer’s disease.

“Findings from this large…study implicate HSV-1 in the development of Alzheimer’s disease and highlight anti-herpetic therapies as potentially protective for Alzheimer’s and related dementia,” the researchers said in the journal BMJ Open.

HSV-2 and varicella-zoster virus infections have also been associated with a heightened risk of Alzheimer’s.

Varicella-zoster virus causes chickenpox and this virus is part of the same family of viruses that cause cold sores and genital herpes. Crucially, varicella-zoster virus can remain dormant in the body and reactivate later in life, causing shingles.

The specific mechanism linking HSV-1 and Alzheimer’s is still unclear, however experts believe inflammation caused by the virus may play a pivotal role.

More research is needed to confirm these findings and to determine the potential of antiviral medications in preventive care.

“However, studies have shown that inflammatory alterations in the brain caused by HSV infection are pivotal in (Alzheimer’s disease) development,” researchers added.