A large U.S. study adds to evidence that the shingles vaccine may also protect the brain. Researchers found that people who received the vaccine had a 24% lower risk of developing dementia than those who did not, although the exact biological mechanism remains unknown.
The study, published in Annals of Internal Medicine, was led by Brown University researchers and analyzed data from more than half a million people. After four years of follow-up, dementia risk was 19% among vaccinated participants, compared with 24% among those who were not vaccinated. The findings are especially notable because the average participant was 79 years old and about two-thirds were women, both groups at higher risk of dementia.
Dementia is an umbrella term for degenerative brain diseases, including Alzheimer’s, that affect memory, thinking and behavior. In Britain alone, about 1 million people live with dementia, and it is the country’s leading cause of death. Shingles itself is caused by the reactivation of the chickenpox virus, which can remain dormant in the body for decades and can cause a painful rash, nerve pain and lasting complications.
Dr. Kaylin Hayes of Brown, one of the study leaders, said, “We still do not know for certain why the risk of dementia is lower among those vaccinated, but we do have several promising directions.” Professor Barak Gaster of the University of Washington said he tells patients the vaccine may help protect brain health, while Professor David Reuben of UCLA warned that the study is observational and that it is too early to change clinical guidance. The researchers say the results do not prove causation, but British and U.S. teams hope to launch large clinical trials to test whether the vaccine truly reduces dementia risk. Earlier research also linked the shingles vaccine to a 50% lower risk of vascular dementia and a 25% lower risk of heart attack and stroke.
