New study shows virus behind cold sores may have link to the development of Alzheimer’s disease

A new study has found the virus responsible for the common cold sore may have a role in the development of Alzheimer’s disease.

A new study has found the virus responsible for the common cold sore may have a role in the development of Alzheimer’s disease.

And scientists believe antiviral treatments may help people to lower the risk of developing the debilitating brain disorder.

The new study in the medical journal BMJ Open, looked at the history of people who have the virus behind cold sores known as herpes simplex 1 (HSV-1).

It matched more than 340,000 people with and without Alzheimer’s and assessed their history of herpesvirus infections using US health insurance data over a 15 year period between 2006 and 2021.

The risk of developing Alzheimer’s increases with age. Based on the study’s data, those with the disease were also 80 per cent more likely to have had an HSV-1 diagnosis.

The study found various infectious agents have been implicated in the development of Alzheimer’s disease.

The most studied of these is HSV-1, which affected more than two-thirds of under 50s around the globe in 2016 alone.

Alzheimer’s is the leading cause of death for Australian women, and is second overall cause of deaths nationally which affects more than 480,000 Australians.

Exactly how HSV-1 and other neurotropic viruses might increase the risk of dementia isn’t clear, the researchers said in the study published Wednesday.

The virus that causes cold sores may be linked to the development of Alzheimer’s disease.

“However, studies have shown that inflammatory alterations in the brain caused by HSV infection are pivotal in [Alzheimer’s disease] development,” they said.

The viral infection spreads through intimate one-to-one contact between people.

Among the 2330 people with a history of HSV-1 infection, (40 per cent) used antiherpetic medication after their diagnosis, which meant they were 17 per cent less likely to develop Alzheimer’s disease than those who didn’t get treatment.

This observational study has no firm conclusions that can be drawn about cause and effect, but they are in line with other studies that exist.

“While the molecular mechanisms remain to be fully elucidated, these results are indicative of a possible role for antiherpetic therapy in mitigating dementia risk,” they said.

“These findings place an even greater emphasis on viewing the prevention of herpes viruses as a public health priority.”

Dr Bryce Vissel, Director of the Centre for Neuroscience and Regenerative Medicine at St Vincent’s Hospital Sydney, said: “We’re not saying viruses explain everything. But they may be central to it. This is no longer a fringe theory — it’s the next phase of Alzheimer’s research, and we’re pursuing it.”

“These viruses are incredibly common. Most people are infected in childhood. They retreat into the nervous system and stay there for life.

“Under certain conditions — stress, inflammation, immune decline — they can reactivate.

“This may trigger an inflammatory cascade in the brain that leads to the synapse loss and memory decline characteristic of Alzheimer’s.”

He added: “If herpesviruses play even a part in causing Alzheimer’s — and if we can intercept that process — then we’re not just talking about understanding the disease. We’re talking about preventing it. That changes everything.”

Professor Anthony Hannan, Group Head of the Epigenetics and Neural Plasticity Group at the Florey Institute of Neuroscience and Mental Health, said it builds on other studies linking these kinds of viral infection to the risk of Alzheimer’s disease.

”It is important now to follow this up with studies to address causation, and mechanisms involved,” he said.

“This study could also lead to future antiviral interventions whose primary aim is to prevent dementia.”

Originally published as New study shows virus behind cold sores may have link to the development of Alzheimer’s disease