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; 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.