To examine whether exposure to anti-herpetic drugs (AHDs: acyclovir, valacyclovir, famciclovir) is associated with reduced risk of Alzheimer’s disease (AD) treatment initiation.

Population-based retrospective matched cohort study.

University Groningen community pharmacy database IADB.nl, covering approximately 125 Dutch pharmacies (1994–2024).

262 757 adults aged 50–80 years without prior dementia or AD treatment. Exposed individuals with antiherpetic prescriptions (n=23 887) were matched 1:10 to unexposed controls (n=238 870) by age, sex and calendar time.

AHDs: acyclovir, valacyclovir, famciclovir.

Initiation of AD drug treatment, defined as at least two prescriptions for rivastigmine, donepezil, galantamine or memantine within 1 year. Cox proportional hazards models estimated HRs with 95% CIs, adjusted for comorbidities and medications. Analyses were stratified by period (1994–2018 vs 2019–2024) and drug type.

During follow-up, 2495 participants initiated AD treatment. The age of the participants was 65 (SD 9), and 59% were female. Any AHD exposure was associated with 90% reduced hazard of AD treatment (HR 0.09, 95% CI 0.07 to 0.13, p

AHD exposure was consistently associated with markedly lower risk of AD treatment initiation, with similar findings observed in recent years. These findings support the hypothesis that herpesvirus reactivation may contribute to AD pathogenesis and suggest antiviral therapy could have preventive implications. Confirmation through prospective studies and randomised trials is needed.