Eosinophilic esophagitis incidence in New Zealand: high but not increasing

Eosinophilic esophagitis (EoE) is an immune-mediated inflammatory condition of the esophagus. Recent literature has shown an increasing incidence of the disease. However, no epidemiological data exist regarding New Zealand rates of EoE. The disease is associated with atopy, and New Zealand's high rate of atopic disease means the disease may be important in our population. We carried out a retrospective study to describe the incidence of EoE in the Wellington region of New Zealand, as well as key histological and clinical factors associated with the disease.

A search was made of laboratory and endoscopic databases in the Wellington region to identify all diagnosed cases in the five years between January 1, 2011, and December 31, 2015. Case notes were examined to determine the key demographic and clinical parameters in the cases. Incidence rates were calculated for each year, and the effects of age group and sex on the incidence rates were analyzed.

We found 152 cases of EoE in the Wellington region with an annual incidence of 6.95 per 100,000 person/years. We found no evidence of a significant difference in incidence rates by year in our study population. There was a significantly lower incidence rate in those aged <16 compared to those aged ≥16 (RR=0.26). Males had a higher incidence rate than females with an estimated rate ratio of 2.45 (p<0.05).

Our results are in contrast to previous reports of increasing incidence rates and may reflect a leveling off of incidence. Further research is needed to determine whether the low incidence in our pediatric age group is due to ascertainment bias or due to a real difference in the epidemiology of EoE in NZ compared to other countries.