Cold Sore Virus Linked to Double the Risk of Dementia, Study Finds
Could a common virus responsible for cold sores play a hidden role in dementia?
A new prospective study from Uppsala University, published in the Journal of Alzheimer’s Disease (2024), suggests that infection with the herpes simplex virus (HSV) may double the risk of developing dementia in older adults.
Why scientists looked at herpes and the brain
Over 55 million people worldwide are living with dementia, a number expected to rise sharply as the population ages. Alzheimer’s disease accounts for about 70% of these cases, but its exact cause remains elusive.
For decades, researchers have suspected that viral infections, including herpes simplex virus type 1 (HSV-1)—the same virus that causes cold sores—might contribute to brain changes leading to Alzheimer’s disease.
Previous studies have shown mixed results. Some found a strong connection between herpes and dementia, while others found none. The Swedish team, led by Dr. Bodil Weidung and Erika Vestin, set out to clarify this link using a uniquely consistent and well-monitored population group.
How the study was done
Researchers followed 1,002 Swedish adults, all aged 70 at the start of the study (2001–2005), for up to 15 years. None had dementia at the beginning.
Blood samples were taken to check for antibodies against HSV and cytomegalovirus (CMV)—another common herpesvirus—to determine who had past infections. The team also analyzed genetic data (especially the APOE ε4 gene, a known Alzheimer’s risk factor) and tracked prescriptions for antiviral drugs.
Over the follow-up period:
7% of participants developed dementia,
4% were diagnosed with Alzheimer’s disease, and
82% tested positive for herpes simplex antibodies.
Key findings: herpes infection doubled dementia risk
People who carried HSV antibodies—meaning they had been infected at some point—had a 2.26 times higher risk of developing dementia than those who were not infected.
Interestingly, the link was specific to dementia in general, not necessarily Alzheimer’s disease alone, though the risk pattern was similar.
The researchers found:
No significant effect from CMV infection,
No clear interaction between HSV and the APOE ε4 gene, and
No strong protective effect from antiviral medication in this group (possibly due to limited use).
What this means and what’s still uncertain
The findings add to growing evidence that herpes simplex may play a role in the complex process leading to cognitive decline. However, the study couldn’t prove causation.
It’s possible that chronic or reactivated HSV infections trigger inflammation in the brain, indirectly contributing to dementia over time.
Because only a small number of participants developed Alzheimer’s, the study may have lacked the power to detect subtler associations. The authors note that randomized clinical trials are needed to test whether antiviral treatment could actually lower dementia risk.
A clue to prevention?
While it’s too soon to recommend antiviral drugs as a preventive measure, these results highlight an intriguing and potentially modifiable risk factor.
If future research confirms that managing HSV infections can reduce dementia risk, simple antiviral treatments or vaccines could become part of prevention strategies for aging populations.
Reference
Vestin E., Boström G., Olsson J., Elgh F., Lind L., Kilander L., Lövheim H., & Weidung B. (2024).
Herpes Simplex Viral Infection Doubles the Risk of Dementia in a Contemporary Cohort of Older Adults: A Prospective Study.
Journal of Alzheimer’s Disease, 97, 1841–1850.
DOI: 10.3233/JAD-230718