Study: Herpes Zoster Is Not Associated With Increased Risk of Dementia

Shingles, also known as herpes zoster, is not associated with an increased risk of dementia, despite scientific speculation that nerve inflammation related to shingles could increase this risk according to the results of a study published in Neurology, the medical journal of the American Academy of Neurology.¹

“As a person’s age increases, so does their risk of dementia, and it’s important to determine which factors may contribute to this risk,” Sigrun Alba Johannesdottir Schmidt, MD, PhD, of Aarhus University Hospital in Denmark, said in a statement.

“Shingles most often affects people over age 50,” she said. “The good news is that our study found it does not seem to increase a person’s risk for dementia.”¹

In the study, investigators reviewed Danish medical registries over a 20-year period. They identified 247,305 individuals who had visited a hospital for shingles or were prescribed antiviral medication for shingles and matched 1,235,890 individuals for age and sex who did not have the disease. The average age was 64 years.¹

Then, investigators determined which individuals developed dementia up to 21 years after their shingles diagnosis. Of those who had shingles, 9.7% developed dementia compared with 10.3% of those who did not have shingles.¹

Additionally, after adjusting for other health conditions, including cancer, diabetes, and traumatic head injury, the investigators found that individuals with shingles had a 7% lower risk of dementia than individuals who did not have shingles.¹

“We were surprised by these results,” Schmidt said.

“The reasons for this decreased risk are unclear, but it could be explained by missed diagnoses of shingles in people with undiagnosed dementia. Shingles vaccination is encouraged for older people because it can prevent complications from the disease, but our study suggests it is unlikely to reduce dementia risk,” Schmidt said.¹

Investigators found that individuals who had shingles that spread to the central nervous system had nearly twice the risk of developing dementia, though they said that these complications are very rare, affecting fewer than 0.1% of individuals with shingles.¹

A limitation of the study was that individuals were identified based on antiviral prescriptions or hospital visits for the disease, so results may be the same for individuals with milder cases and those who were not treated for the disease.¹

The study was supported by the Edel and Wilhelm Daubenmerkls Charitable Foundation.¹

Approximately 1 in every 3 individuals in the United States will develop shingles within their lifetimes, with an estimated 1 million getting shingles each year, according to the CDC.²

has Anyone who has had the chickenpox is at risk of developing shingles, but the risk of shingles with more serious complications increases with age.²

Shingles can lead to complications involving the eyes, including blindness, and approximately 1 in 10 individuals develop nerve pain that lasts for months or years after the rash goes away. More rarely, shingles can lead to encephalitis, hearing problems, pneumonia, and even death.²

Reference

1. Does shingles increase a person’s risk of dementia? EurekAlert. News release. June 8, 2022. Accessed June 10, 2022. https://www.eurekalert.org/news-releases/954913

2. CDC. Updated February 3, 2022. Accessed June 10, 2022. https://www.cdc.gov/shingles/index.html#:~:text=About%201%20out%20of%20every,Even%20children%20can%20get%20shingles