Anti-herpetic treatment reduces dementia risk: A systematic review and meta-analysis

BackgroundHuman herpesvirus (HHV) infections, particularly for herpes simplex virus (HSV) and varicella-zoster virus (VZV), may increase dementia risk, yet the protective effects of anti-herpetic medications remained unclear.ObjectiveThis systematic review and meta-analysis of observational studies aimed to examine the association between anti-herpetic medications and dementia, focusing on HSV or VZV-related infections.MethodsThis study followed PRISMA guidelines (CRD42022368318). Cohort or nested case-control studies published from databases' inception to December 2024 were systematically searched in PubMed, MEDLINE, Embase, Cochrane Library, PsycINFO, and Web of Science. Eligible studies evaluated anti-herpetic medications (e.g., acyclovir, famciclovir, ganciclovir, valacyclovir, valganciclovir) and dementia risk in non-demented adults aged ≥50. Pooled adjusted hazard ratios (aHR) and 95% confidence intervals (CIs) were analyzed using random-effects models. Subgroup and meta-regression analyses were performed to explore potential sources of heterogeneity and effect modifiers.ResultsFourteen cohort studies involving more than 10 million older adults were included. To demonstrate the effects of anti-herpetic medications in various clinical scenarios, the meta-analysis compared: diagnosed and treated versus diagnosed but untreated (aHR=0.77, 95% CI: 0.67-0.89); treated versus untreated regardless of diagnosis (aHR=0.90, 95% CI: 0.87-0.94); and diagnosed and treated versus neither diagnosed nor treated (aHR=0.87, 95% CI: 0.78-0.97). Subgroup analysis and meta-regression identified infection severity as a significant modifier (p < 0.0001), explaining 89.01% of heterogeneity.ConclusionsThis systematic review and meta-analysis reveals notable protective effect of anti-herpetic medication usage on dementia, and the effect is especially pronounced in patients with severe alpha herpesvirus infections.