Identification of herpes zoster high-risk group using Charlson comorbidity index: A nationwide retrospective cohort study.

The incidence of herpes zoster (HZ) is mainly affected by age. Various comorbidities could influence the risk of HZ, but a general guideline for evaluating their effect on HZ is lacking. The purpose of this study was to determine whether the Charlson comorbidity index (CCI) is useful in evaluating the risk of HZ in the general population. This retrospective cohort study analyzed data from 1 016 580 random multistage representative samples in Korea, recorded from 2004 to 2013 in the South Korean National Health Insurance Service-National Sample Cohort database. We calculated the baseline CCI score of comorbidities and compared the hazard ratio (HR) of HZ according to the calculated CCI scores. A total of 340 124 eligible subjects aged 40-79 years and 35 874 HZ patients were identified. After adjustment of age, sex and income, the HR of HZ and odds ratio of postherpetic neuralgia in the CCI score of 1 or more group was found to be significantly higher than that of the CCI score 0 group. Compared with the 60s age group with a CCI score of 0, the 50s age group with a CCI score of 1 had a higher risk of HZ, and the 40s age group with a CCI score of 3 or more had a similar risk of HZ. Scoring systems of comorbidities such as the CCI could be useful in identifying the high-risk group for HZ, especially among the 40-59-year age group. Further studies are required to establish the usage of a HZ-specific comorbidity scoring system in a large multinational population.