A recent study published in the British Medical Journal has highlighted a potential link between a common viral infection and an increased risk of Alzheimer’s disease. Herpes simplex virus type 1 (HSV-1), the virus responsible for cold sores, has been associated with an 80 percent higher risk of developing Alzheimer’s dementia.
Researchers analyzed medical records from over 300,000 individuals aged 50 and above, splitting participants into two equal groups based on whether they had Alzheimer’s disease. The findings revealed that 1,507 individuals (0.44%) with Alzheimer’s had a history of HSV-1 infection, compared to 823 individuals (0.22%) without Alzheimer’s. This suggests a significant association between HSV-1 infection and Alzheimer’s risk.
Importantly, this elevated risk remained consistent even after accounting for other factors, including the presence of two copies of the APOE4 gene, a well-known genetic risk factor for Alzheimer’s. Furthermore, those who received antiviral treatments for HSV-1 were 17 percent less likely to develop Alzheimer’s compared to those who did not receive such treatments.
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Despite these notable findings, experts urge caution. Dr. Sheona Scales, director of Research at Alzheimer’s Research UK, emphasized that the study relied on self-reported health records and administrative data, which may not capture all HSV-1 infections, particularly as many infected individuals show no symptoms. She also noted the difficulty in diagnosing Alzheimer’s, especially in its early stages.
While HSV-1 infection is widespread and does not guarantee the development of Alzheimer’s, the study raises important questions about how viral infections might contribute to brain inflammation and later cognitive decline. Dr. Scales added that although lifestyle and environmental factors are known to influence dementia risk, more evidence is needed before infections can be considered a direct cause.
Alzheimer’s disease remains the most common form of dementia worldwide, accounting for up to 80 percent of cases. This research adds to a growing body of evidence suggesting infectious agents could play a role in its development, but further studies are essential to fully understand these complex interactions.