Dear Doctor: Pretty much everyone I know gets cold sores from time to time. Now I see a study saying that cold sores are somehow connected to Alzheimer's. Can you explain?
Dear Reader: As researchers have worked to understand Alzheimer's disease, the results of some studies have suggested a link to certain infections, including oral herpes, or cold sores. Pneumonia, chronic inflammation and infection with spirochete bacteria, which causes Lyme disease and can be associated with some types of gum disease, were implicated as well. Initially scientists noticed a higher incidence of Alzheimer's among people who also reported having contracted one or more of these infections. It was unclear whether the infections themselves were linked to Alzheimer's, or whether people with Alzheimer's were simply more prone to infection.
Now, a new study draws a clearer line between Alzheimer's disease, a devastating form of dementia, and the herpes simplex virus 1, which causes cold sores. Published last fall in the journal Frontiers in Aging Neuroscience, the study cited being infected with herpes simplex virus 1, also known as HSV1, as a major risk factor for developing Alzheimer's disease. In the new study, which consists of a review of decades of research, including her own, a scientist from England's University of Manchester thinks that up to half of all cases of Alzheimer's disease have a direct connection to HSV1.
An estimated 5.7 million Americans are now living with Alzheimer's, with a new diagnosis being made every minute. At this time there is no cure for the disease, and no reliable ways to manage it. When it comes to HSV1, between 50 and 80 percent of adults in the United States are believed to be infected with the virus. It is spread through contact with the oral secretions of someone who has an active infection, whether through direct contact or by sharing an object, like a glass or a toothbrush. Once infected, a person has the virus for life. However, much of the time it lies dormant. Some people can have the virus and never develop symptoms. Others can have outbreaks that range from occasional to frequent.
The thinking behind the link between HSV1 infection and Alzheimer's is that, as our immune systems weaken with age, the oral herpes virus is able to travel to the brain. Another piece of the puzzle is a version of a gene known as APOE, which plays a role in the manufacture of lipoproteins. It appears that the herpes virus either reactivates more frequently in people who are carriers of that particular gene variant, or that the reactivation is more harmful. Either way, the result is believed to cause changes within the brain tissue that lead to Alzheimer's.
Considering how many of us get cold sores, these new developments can be unnerving. That's why it's important to note that these findings are still preliminary, and more research is needed. The very good news is that, should the HSV1 theory prove to be correct, it gives scientists their first real line of attack against Alzheimer's disease, in the form of antiviral drugs. It even opens the door to the development of an anti-Alzheimer's vaccine.
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