Results from a study of herpes zoster incidence following periods of acute stress in a large cohort of patients suggest the conventional wisdom on this subject may be wrong.
Herpes zoster, a painful rash caused by reactivation of the varicella zoster virus, is associated with two key risk factors: age (risk increases significantly as patients get older) and a weakened immune system. Among other possible causes for herpes zoster reactivation and progression, one of the most commonly suggested is psychological stress. Although it is widely believed to be a trigger, there is little research to support this.
To evaluate whether psychological stress is a risk factor for herpes zoster in adult patients, the authors of research presented at IDWeek 2014 evaluated medical claims data for nearly 40,000 adult patients age 25 years and older who experienced acute psychological stress to see if there was an increase in herpes zoster events during the 3-month “risk window” after the stressful event compared to a 3-month “control window” prior to the stressful event.
For the study, acute psychological stress was defined as an “unexpected death or catastrophic health event occurring in a previously healthy spouse.” The researchers used self-controlled case series methods to assess for increases in herpes zoster events. To control for “changes in health seeking that might occur in persons experiencing stress,” the authors also used Poisson regression to assess for increases in herpes zoster “as a proportion of all outpatient health care services during the risk as compared to control window.”
To validate their definition of stress for this study, the authors also compared the number of mental health visits (based on ICD-9 codes) during the 3-month risk window compared to the number of visits during the control window, to determine whether “the proportion of these visits increased during the risk window compared to the control window.”
The authors reported that in patients age 60 or younger (N=21,405), there were 24 herpes zoster events during the control window, compared to 22 events during the 3-month risk window. In patients who were older than age 60 (N=18,406), there were 54 events during the control window, compared with 37 during the risk window.
Overall, the herpes zoster relative incidence in this patient population did not increase during the 3-month risk window compared to the 3-month control window (0.76; 95% CI, 0.54-1.06). These numbers held true when looking at risk periods of 30, 60, and 120 days. There was no increase in herpes zoster events as a proportion of all health care services used by the patients in this cohort during the risk window compared to the control window.
Thinking that perhaps the extreme grief of losing a spouse would be more of a trigger for herpes zoster, the authors looked at the numbers for the subset of patients whose spouse had died but found no increase in risk.
Perhaps not surprisingly, the authors reported there was an increase in the number of stress-related mental health visits during the risk window compared to the control window: 750 vs. 454 in patients younger than age 60, and 289 vs. 141 in patients age 60 and older. The number of mental health visits also increased as a proportion of all health care services used during the study period.
Limitations of this study identified by the authors include the use of administrative data rather than medical records, and the inability to validate the diagnostic codes with medical records.
Based on these results, the authors reported finding no association between psychological stress and herpes zoster outbreak, and that further study is needed to identify additional risk factors for herpes zoster and molecular pathophysiological triggers for reactivation of the varicella zoster virus.