Cold Sore Oral Herpes (HSV 1) Linked to Alzheimer’s Dementia

One dementia risk reduction strategy I covered in my book How Not to Age is to be careful who you smooch. Amyloid beta, the protein associated with Alzheimer’s plaques in the brain, is strongly conserved throughout evolution, the human variant of which dates back at least 400 million years and is today found in most vertebrate species. It must have some sort of beneficial function. Survival of the fittest has historically been less about the dynamics of predator against prey than about the starkest us versus them: the microbial threats that prey on us all. Amyloid beta may be part of our immune system, an antimicrobial peptide that protects us against brain infections. Amyloid beta was shown to be antibacterial, antifungal, and antiviral against a range of common pathogens. For example, temporal lobe samples from Alzheimer’s brains are better at killing off Candida yeast, a cause of fungal meningitis, than samples from the same part of the brain from those who died from other causes.

Amyloid beta also binds to herpes simplex virus 1 (HSV-1). HSV-1 is the virus that normally causes cold sores (also known as fever blisters) but can also infect the brain. So, might amyloid beta contribute to protecting viral entrapment? Is it possible that infection with this common virus could trigger amyloid deposition in your body’s attempt to suppress it, but thereby inadvertently lead eventually to Alzheimer’s disease?

It seemed a bit far-fetched when I first heard about it, but I was surprised to find about 100 publications linking HSV-1 infection to Alzheimer’s disease in medical literature. For example, this study following tens of thousands of individuals found that those with either oral herpes (HSV-1) or genital herpes (HSV-2) were more than twice as likely to develop dementia during the 16-year follow-up period. Even more convincing (and offering a dose of good news), researchers found that those with HSV who took antiviral medications (like acyclovir) appeared 90 percent less likely to develop dementia compared to those whose HSV was left untreated. Unfortunately, there are not yet licensed vaccines to prevent getting infected in the first place with HSV-1. But measures you can take to reduce your risk include avoiding kissing or sharing utensils, cups, water bottles, towels, or lip balm with those who have an active oral infection, though asymptomatic viral shedding can also occur.