Study Shows Shingles Infection Could Be Associated With Dementia

New study findings assessed the association between a herpes zoster (HZ) diagnosis and its treatment in relation to incident of dementia among older individuals. The retrospective matched cohort study was conducted following the release of conflicting evidence that suggested HZ is associated with elevated risk of dementia and certain anti-viral medications relate to lower risk.¹

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Dementia is a progressive brain disorder that impacts cognition and memory, accounting for a large sum of deaths worldwide.¹ According to the Alzheimer’s Association, approximately 7 million individuals in the US are living with Alzheimer and dementia, and the number is expected to reach nearly 13 million by 2050.² Among the various risk factors tied to dementia, studies suggest that HZ could also play a role, but has not yet been confirmed.¹

HZ, commonly known as shingles, is caused by the reactivation of the varicella-zoster virus (VZV). The virus remains dormant for many years, but when reactivated it travels along sensory nerve fibers, resulting in shingles infection. The virus causes a development of painful, blistering rashes in a dermatomal distribution.³ Study authors noted that the prevalence of HZ is about 0.2% to 2% in the general population.⁴

According to the study authors, previous studies have found that HZ relates to an elevated risk of subsequent dementia diagnosis, with hazard ratios extending from 1.1 to 2.8. However, additional studies found that use of HZ anti-viral medications was linked to lower risk of dementia diagnosis with hazard ratios of 0.55 and 0.79. To evaluate the association, researchers conducted a study using ICD-9 and ICD-10 diagnosis codes in electronic medical records from 2000-2019 among members of the Kaiser Permanente Northwest (KPNW) 50 years and older that had a HZ diagnosis.¹

When conducting the study, researchers individually matched each person with HZ with 3 patients without HZ, as of the exposed individuals index date. Additionally, antiherpetic medication orders were evaluated 1 month before the index date to 12 months after the index date. The study authors noted that this was to ensure that the medication was prescribed for HZ, among individuals that were exposed or had a confirmed diagnosis.¹

“Among subjects with HZ, we examined antiviral medication dispensing in relation to dementia diagnosis, and we compared demographic and clinical characteristics between persons with and without antiviral medication use,” said the study authors.¹

The population-based retrospective cohort study included a total of 101,328 individuals. Among the total group, over 25,000 individuals had HZ and a researchers matched a comparison sample of over 75,000 individuals without HZ.¹

The results displayed that over a median follow-up of 4.8 years, approximately 6000 individuals developed dementia. Individuals diagnosed with HZ were not connected with a higher hazard of dementia in the primary analysis (0.99, 95% CI 0.93–1.05). In the univariate analysis, the hazard ratio of any antiherpetic medication among individuals with HZ was 0.79 and 0.88 after demographic and clinical factor adjustments. The study authors noted that dementia was not linked with duration of medication use or dosing.¹

“We found little evidence for an association between HZ diagnosis and dementia in the overall population, though women may have slightly elevated risk a few years after the HZ episode,” said the study authors.¹

The findings suggest that an HZ diagnosis and dementia was not directly associated and use of antitherapeutic medication prescribed for HZ related to lower risk of subsequent dementia in some subgroups.¹

REFERENCES

1. Weinmann S, Rawlings A, Koppolu P, Rosales AG, Prado YK, Schmidt MA. Herpes zoster diagnosis and treatment in relation to incident dementia: A population-based retrospective matched cohort study. PLoS One. 2024;19(1):e0296957. Published 2024 Jan 25. doi:10.1371/journal.pone.0296957

2. Alzheimer’s disease facts and figures. Alzheimer’s Association. 2024. Accessed November 14, 2024. https://www.alz.org/alzheimers-dementia/facts-figures.

3. Antivirals against DNA viruses (hepatitis B and the herpes viruses). Science Direct. News release. October 2004. Accessed November 14, 2024. https://www.sciencedirect.com/science/article/abs/pii/S1471489204001274

4. Chen J, Lei D, Cao P, He J, Zhang L. Efficacy and safety of brivudine for the treatment of herpes zoster: a systematic review and meta-analysis. J Dermatolog Treat. 2024;35(1):2355256. doi:10.1080/09546634.2024.2355256.