Background/Purpose: To determine the incidence, time trends and, severity of herpes zoster in a population-based incidence cohort of patients with polymyalgia rheumatic (PMR) compared to individuals without PMR from the same population.

Methods: All incident cases of PMR in a geographically-defined area diagnosed between 1990 and 2014 were identified. Patients were followed by retrospective chart review until death, migration, last contact or December 31, 2015. The medical records of all patients with codes for herpes zoster (HZ) were reviewed to confirm the diagnosis, to ascertain the extent of skin disease (single or multidermatomal lesions) and to determine the outcome of HZ infection (extent of organ involvement/ complications and hospitalizations).

Results: The study included 541 patients with PMR and 541 subjects without PMR. The average age at PMR incidence (index date for the non-PMR cohort) was 74 years, and 349 (65%) subjects were female in each cohort. The median follow up was 8.5 years in PMR group and 7.3 years in non-PMR groups. During follow-up, 67 patients with PMR and 41 patients without PMR developed HZ. The cumulative incidence of HZ was higher in PMR patients compared to non-PMR subjects (14.3%±1.8 at 10 years in PMR vs. 10.4%±1.8 at 10 years in non-PMR; p<0.05; Figure 1). Therefore, patients with PMR were more likely to develop HZ than those without PMR (hazard ratio: 1.51; 95 % confidence interval: 1.03 – 2.23). HZ rates by decade among patients with PMR were 1.0, 2.0 and 1.2 per 100 person-years [py] compared to 0.6, 1.6 and 0.9 per 100 py among non-PMR in 1990-1999, 2000-2009 and 2010-2016, respectively. The decline in HZ incidence after year 2006 likely reflects the introduction and use of zoster vaccine in this time period (Figure 2).  Complications of HZ occurred at a similar rate in both cohorts. Rate of vision impairment and multidermatomal involvement was higher in PMR group but this did not reach statistical significance.

Conclusion: The incidence of HZ in PMR is increased compared to the general population. Patients with PMR should be evaluated for shingles vaccination. Further research needs to be done in order to understand the determinants of increased incidence of HZ in PMR patients.