A new study published in BMJ Open has found that infection with the herpes simplex virus type 1 (HSV-1) – responsible for the so-called "cold sores" – may increase the risk of developing Alzheimer's disease by 80%.
But the use of antiviral drugs such as acyclovir, which are widely used against HSV-1, can reduce this risk by 17%.
What did the study show?
Data from 344,628 people with Alzheimer's and an equal number of individuals without the disease were analyzed.
HSV-1 was present in 0.44% of Alzheimer's patients, versus 0.24% in those without the disease.
931 of 2,330 patients with HSV-1 had used antiviral medications after diagnosis.
The authors suggest that treating the herpes virus may be a promising way to reduce the risk of Alzheimer's and other forms of dementia.
How does HSV-1 affect the brain?
HSV-1 can lie dormant in the body for years before "reawakening."
This virus is associated with amyloid plaque-like formations, a typical sign of the brains of people with Alzheimer's.
HSV-1 can also promote chronic brain inflammation, an important factor in the development of dementia.
What about other viruses?
The researchers also analyzed the role of:
HSV-2 (genital herpes)
Varicella zoster (chickenpox and shingles virus)
Cytomegalovirus (CMV)
All of these have been linked to increased risk of Alzheimer's, but their role remains less clear.
Comments from experts
Prof. Tara Spiers-Jones (University of Edinburgh):
"This is a good study that strengthens the link between viruses like HSV-1 and Alzheimer's. But it should be noted that the vast majority of people with HSV-1 do not develop Alzheimer's."
Dr. David Vickers (University of Calgary):
"The role of HSV-1 in this study is exaggerated. It is absent in over 99% of Alzheimer's cases. And the risk reduction with antivirals only translates into a delay in disease onset by 9 months."
Dr. Richard Oakley (Alzheimer's Society):
“The study shows correlation, not causation. The data comes from insurance records that may not always be accurate.”
Dr. Sheona Scales (Alzheimer's Research UK):
"Viral infections are not yet included as official risk factors for dementia. Much more research is needed."
What conclusions can we draw?
Infection with HSV-1 is very common, but it does not automatically mean that someone will develop Alzheimer's.
Antiviral drugs may offer partial protection, but the impact is modest.
The link between viruses and Alzheimer's is complex and not yet fully understood.
Should we take action?
✅ What about individuals with recurrent herpes infections: the use of antiviral medications may have secondary benefits for brain health.
🚫 No to the mass use of antiviral drugs for Alzheimer's prevention, without clear guidance from the medical community.
This study reinforces the hypothesis that viral infections may contribute to neurodegenerative diseases, but caution is needed in interpretation. Future research will be essential to understand how and to what extent viruses affect brain aging. /Express newspaper/
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