Risk of dementia following herpes zoster infection among patients undertreatment versus those not: A systematic review and meta-analysis

Background and Aims: According to the previous studies, herpes zoster (HZ) has been associated with cognitive function and dementia. There is a hypothesis claiming that dementia risk may be reduced by receiving the antiviral treatment for HZ. The purpose of this systematic review and meta-analysis was to shed light on the association between dementia and HZ in individuals receiving and not receiving antiviral medications. Methods: Studies investigating the association between HZ and dementia were identified through a systematic search in PubMed/MEDLINE, Scopus, Embase, Google Scholar, and Cochrane Library databases from January, 2000 to April, 2022. Data on the risk of dementia in HZ-infected patients under and not under antiviral treatment were extracted. The meta-analysis was conducted using a random-effects model. The modified ROBIN-I tool was used to evaluate the risk of bias assessment. By utilizing the funnel plots, publication bias was investigated. Results: Six cohort studies on 538,531 patients were included. The overall risk of bias assessment was moderate. According to evidence-based cohort studies, there was a significant direct association between HZ and risk of dementia in patients with HZ, who did not receive antiviral treatments (hazard ratio [HR]: 1.15, 95% confidence interval [CI]: 1.03 to 1.28, p = 0.01). On the other hand, there was an inverse relationship between HZ and risk of dementia among patients with HZ, who received antiviral treatments (HR: 0.68, 95% CI: 0.59 to 0.77, p < 0.001). Conclusions: This study demonstrated that antiviral therapies may significantly lower the risk of dementia in patients with HZ. This study also confirmed that patients with HZ, without receiving antiviral therapies, may have an increased risk of developing dementia. Further longitudinal research is warranted in this area.