Incident Herpes Zoster and Risk of Dementia: A Population-Based Danish Cohort Study.

Herpes zoster is not associated with increased risk of dementia, and contrary to expectation we found a small decrease in risk. The explanation for this finding is unclear, and systematic errors should be considered. Patients with central nervous system involvement had almost two-fold increased relative risk of dementia. The population attributable fraction of dementia due to this rare complication is estimated at 0.014%. Therefore, universal vaccination against varicella-zoster virus in the elderly is unlikely to reduce dementia risk.