More Evidence That Viral Infections Can Be a Trigger for Dementia

In prior studies, researchers have reported that infection with neurotropic herpesviruses — particularly herpes simplex virus (HSV), varicella-zoster virus (VZV), and human herpesvirus-6 (HHV-6) — and more recently, SARS-CoV-2, might be a risk factor for developing Alzheimer disease (AD) and other forms of dementia. However, confounding factors complicate these associations, and mechanisms to explain excess risk have not been elucidated.

Four new studies add to the evidence about viral risk factors. In a study that largely avoided the possibility of confounding, receiving a shingles vaccine markedly lowered risk for developing dementia (NEJM JW Gen Med May 15 2025 and Nature 2025; Apr 22 [e-pub]). Another study showed that infection of vario…