Shingles, a painful condition triggered by the reactivation of the chickenpox virus, manifests as a blistering rash on one side of the body or face due to nerve inflammation. Scientists have theorized that this inflammation could potentially heighten the risk of dementia in individuals. Nevertheless, a recent study has revealed that there is no link between shingles and an elevated risk of developing dementia. This study was published in the online edition of Neurology®, the official journal of the American Academy of Neurology, on June 8, 2022.
The increase in dementia risk with age is well-documented, highlighting the necessity to explore factors that may influence this risk, explained Sigrun Alba Johannesdottir Schmidt, MD, PhD, from Aarhus University Hospital in Denmark. Given that shingles predominantly affect individuals over 50, it is reassuring from our research that it does not seem to amplify the risk for dementia.
In conducting this study, Danish medical registries were scrutinized over two decades to identify 247,305 individuals who had either been hospitalized for shingles or had received antiviral treatment for the condition, alongside 1,235,890 individuals who had not been diagnosed with shingles, matched for age and sex. The mean age among these individuals was 64 years.
The research aimed to track the development of dementia in these participants up to 21 years following a diagnosis of shingles. Among those who had experienced shingles, 9.7% went on to develop dementia, compared to 10.3% among those who had not had shingles.
Even after accounting for other health issues such as diabetes, cancer, and head injuries, the findings indicated that individuals with shingles had a 7% lower risk of developing dementia compared to those without the condition.
“These findings were unexpected,” Schmidt remarked, noting the unclear reasons behind the reduced risk. One possible explanation might be the underdiagnosis of shingles in individuals with undiagnosed dementia. Although the shingles vaccine is recommended for the older adults to prevent disease complications, this study suggests it may not influence dementia risk.
The research did, however, uncover that individuals who experienced shingles spreading to the central nervous system were nearly twice as likely to develop dementia, though Schmidt pointed out that such cases are sporadic, affecting less than 0.1% of those with shingles.
A noted limitation of the study was its reliance on hospital records and antiviral prescriptions to identify participants. It may not fully represent individuals with less severe shingles or those who do not seek treatment.
More information: Sigrun Alba Johannesdottir Schmidt et al, Incident Herpes Zoster and Risk of Dementia A Population-Based Danish Cohort Study, Neurology. DOI: 10.1212/WNL.0000000000200709
Journal information: Neurology Provided by American Academy of Neurology
