A new study has found a possible link between cold sores and Alzheimer’s disease, but experts say there’s no reason for alarm.
The virus that causes cold sores, herpes simplex virus type 1 (HSV-1), may play a small role in the development of Alzheimer’s, but the research is far from conclusive.
HSV-1 is extremely common.
The World Health Organization estimates that nearly two-thirds of people under age 50 worldwide carry the virus, often without knowing it. The initial infection might cause symptoms like fever, headache, and painful blisters around the mouth.
After that, the virus usually stays dormant in the body, only reactivating from time to time—sometimes causing cold sores, but often showing no symptoms at all.
In the new study published in BMJ Open, researchers looked at data from over 340,000 adults aged 50 and older in the United States.
They compared people diagnosed with Alzheimer’s disease to those without it, matching them by age, sex, and location to reduce bias. They found that people with a recorded HSV-1 diagnosis had an 80% higher relative risk of developing Alzheimer’s.
However, the actual number of people with a known HSV-1 diagnosis in both groups was very low—less than half a percent—so the absolute risk remains small.
Interestingly, the study also found that people who were treated with antiviral medication for HSV-1 had a slightly lower risk of developing Alzheimer’s disease. But because HSV-1 is so underdiagnosed—especially when it causes few or no symptoms—many people in the study likely had the virus but weren’t recorded in the data.
This isn’t the first time scientists have looked into the idea that HSV-1 might be involved in Alzheimer’s. Some past studies found traces of HSV-1 in the brains of people who had Alzheimer’s, and lab research has shown the virus might trigger some of the harmful brain changes seen in the disease. Still, none of this proves that HSV-1 actually causes Alzheimer’s.
Experts stress that Alzheimer’s is a complex disease, influenced by many factors like age, genetics, heart health, lifestyle, and education. HSV-1 may be a small piece of the puzzle, but it’s unlikely to be the main cause.
If you get cold sores, there’s no need to worry. Most people with HSV-1 will never develop Alzheimer’s. What we do know is that staying physically active, eating well, getting good sleep, and staying socially and mentally engaged can help keep your brain healthy as you age.
