Risk of herpes zoster among diabetics: a matched cohort study in a US insurance claim database before introduction of vaccination, 1997–2006

PURPOSE: To assess whether diabetes is a risk factor for herpes zoster (HZ). METHODS: We conducted a retrospective cohort study using the Integrated Health Care Information Services database, during the period 1997–2006. A type I diabetes cohort, a type II diabetes cohort and two non-diabetic cohorts matched for date of enrolment and duration of follow-up were defined. HZ and diabetes were defined using a combination of ICD-9 and prescription drug codes. Individuals with immunosuppressive conditions or treatments were excluded. Cox Proportional Hazards regression analysis using a stepwise method with backward elimination was applied to estimate the hazard ratios (HR) of HZ, including age, gender and co-morbidities as covariates. RESULTS: The study population comprised 380,401 and 20,397 type II and type I diabetic subjects respectively, as well as 1,521,604 and 81,588 matched controls. The median ages were 55, 35, 33 and 29 years, respectively. HZ incidence was 4.59, 2.13, 1.97, and 1.82 per 1,000 person-years, respectively. There was no evidence of an impact of type I diabetes on the risk of HZ. Type II diabetes was associated with an increased risk for HZ in subjects ≥65 (HR 3.12; 95 % CI 2.77–3.52, adjusted for gender) and in subjects between 40 and 64 (HR 1.51; 95 % CI 1.42–1.61) years of age. Cardiac disease and chronic pulmonary disease were also risk factors (HR 1.92; 95 % CI 1.73–2.13 and HR 1.52; 95 % CI 1.38–1.67) in non-diabetic subjects. CONCLUSIONS: This study suggests that type II diabetes is associated with an increased risk of developing HZ, which was particularly high in adults 65 years and older and moderately increased in adults under 65 years of age. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s15010-014-0645-x) contains supplementary material, which is available to authorized users.