Increased Risk of Herpes Zoster in Young and Metabolically Healthy Patients with Inflammatory Bowel Disease: A Nationwide Population-Based Study

Background/Aims: The risk of herpes zoster (HZ) among patients with inflammatory bowel disease (IBD) remains unclear in terms of age and metabolic comorbidities, including diabetes mellitus, hypertension, or dyslipidemia. We conducted a nationwide population-based study to investigate the risk of HZ in patients with IBD. Methods: From 2010 to 2013, a retrospective study was performed using claims data in Korea. We compared the incidence of HZ between 30,100 IBD patients (10,517 Crohn's disease [CD] and 19,583 ulcerative colitis [UC] patients) and 150,500 non-IBD controls matched by age and sex. Results: During a mean follow-up of 5.0 years, incidence rates of HZ (per 1,000 person-years) were 13.60, 14.99, and 9.19 in the CD, UC, and control groups, respectively. The risk of HZ was significantly higher in patients with CD (adjusted hazard ratio [HR], 2.13; p<0.001) and UC (adjusted HR, 1.40; p<0.001) than in the controls. The impact of CD on developing HZ was significantly more prominent in younger patients (adjusted HR, 2.61 for age <15, whereas 1.39 for age >= 60; interaction p=0.001) and in patients without metabolic comorbidities (adjusted HR, 2.24, whereas 1.59 in those with metabolic comorbidities; interaction p=0.015). Moreover, the impact of UC on developing HZ significantly increased in younger patients (adjusted HR, 2.51 in age <15, whereas 1.22 in age >= 60; interaction p=0.014) and patients without metabolic comorbidities (adjusted HR, 1.49 whereas 1.16 in those with metabolic comorbidities; interaction p<0.001). Conclusions: IBD was associated with an increased risk of HZ, especially in younger patients without metabolic comorbidities.