HSV-1 Infection Linked to Increased Alzheimer's Risk; Antiviral Treatment May Help: Study

A new study published in the British Medical Journal showed that individuals diagnosed with herpes simplex virus type 1 (HSV-1), which causes cold sores, had a higher risk of later developing Alzheimer's disease. However, the study also revealed that those who received antiherpetic medications experienced a reduced risk of Alzheimer's. 

Between 60% and 80% of dementia cases are caused by Alzheimer's disease (AD), a chronic, slowly progressing, degenerative illness that results in long-term healthcare costs. As the world's population ages, it is anticipated that the incidence of AD will continue to grow in the absence of disease-modifying therapies. The recent identification of Aβ peptide's antibacterial function linked foreign infections to the onset of AD. Amyloid-β (Aβ) plaques and τ neurofibrillary tangles are histological hallmarks of AD and associated dementia, which are characterized by toxic protein aggregates.

The most researched contender among the probable infectious agents, namely herpesviruses, is herpes simplex virus type 1 (HSV-1). There is increasing evidence that herpesviruses contribute to the development of Alzheimer's disease and that people using antiherpetic drugs have a lower chance of developing AD. Using extensive administrative claims data from the USA, this study intends to examine the relationship between HSV-1 infection and AD and AD-related dementia (ADRD) and evaluate the possible advantages of antiherpetic drugs for patients with HSV-1.

The patients with AD aged ≥50 years who were diagnosed between 2006 and 2021 were selected from the IQVIA PharMetrics Plus claims database for a matched case-control study. The subjects with AD and controls were matched 1:1 based on factors such as age, sex, area, year of database entry, and number of medical visits.

There were 344,628 AD case-control couples in the research. When compared to 823 (0.24%) controls, 1507 (0.44%) AD patients had a history of HSV-1 diagnosis. AD was shown to be linked to HSV-1 diagnosis. Compared to patients without antiherpetics, individuals with HSV-1 who took them had a lower risk of developing AD.

Overall, this study demonstrated a link between symptomatic HSV-1 infection and AD and highlighted antiherpetic medications as possibly preventive against AD. The need of considering herpesvirus prevention as a public health priority is further highlighted by these findings. 

Source:

Liu, Y., Johnston, C., Jarousse, N., Fletcher, S. P., & Iqbal, S. (2025). Association between herpes simplex virus type 1 and the risk of Alzheimer’s disease: a retrospective case-control study. BMJ Open, 15(5), e093946. https://doi.org/10.1136/bmjopen-2024-093946