Association of physical trauma with risk of herpes zoster among Medicare beneficiaries in the United States.

Risk factors for herpes zoster (HZ) are poorly defined. An age-matched, case-control study was conducted to assess the effect of physical trauma on HZ, using Medicare data. HZ cases were 3.4 times as likely as controls to have experienced trauma in the week before HZ onset, but the magnitude of the association between trauma and HZ declined over time. Cases who had cranial HZ were >25 times as likely as controls to have had cranial trauma in the week before HZ onset. Therefore, recent trauma can be a trigger for HZ.