Herpes Viruses and Senile Dementia: First Population Evidence for a Causal Link

Three articles have very recently appeared that are of especial relevance to the causes of
dementia and its potential treatment. The first two (Tsai et al., published in PLoS One in
November 2017, and (Chen et al., published in the January/February 2018 issue of Journal of
Clinical Psychiatry) demonstrate an increased risk of subsequent senile dementia (SD)
development in patients with acute varicella zoster (herpes zoster) infection. These articles
present data highly relevant to the third, and most important, paper – by Tzeng et al., published
online in the journal Neurotherapeutics at the end of February 2018. These authors report that
infection with a different herpes virus, herpes simplex virus type 1 (HSV1), leads to a similarly
increased risk of later developing SD. Further, when the authors looked at patients treated
aggressively with antiherpetic medications at the time, the relative risk of SD was reduced by a
factor of 10. It should be stressed that no investigations were made on subjects already suffering
from SD, and that those treated were the few rare cases severely affected by HSV. Nonetheless,
antiherpetic medication prevented later SD development in 90% of their study group. These
articles provide the first population evidence for a causal link between herpes virus infection and
senile dementia.