Prevalence of esophageal eosinophilia varies by climate zone in the United States.

Objectives: The epidemiology of eosinophilic esophagitis (EoE) is rapidly evolving, and differences in climate could impact the prevalence of EoE. We aimed to examine the association between esophageal eosinophilia and climate zones in the United States.

Methods: This was a cross-sectional study of esophageal biopsies from 2008 to 2010 in a large US pathology database. Cases were patients with esophageal eosinophilia; controls had normal esophageal biopsies. A Köppen-Geiger (K-G) climate class was assigned to each patient, and the association between case-control status and the main K-G climate type (tropical, arid, temperate, or cold) was assessed.

Results: A total of 233,649 patients were included, 71,948 (30.8%) with normal esophageal biopsies and 9,995 (4.3%) with esophageal eosinophilia. Using the temperate zone as the referent and after multivariable analysis, the odds of esophageal eosinophilia were highest in the cold climate zone (odds ratio (OR)=1.39, 95% confidence interval (CI): 1.34-1.47), compared with the tropical zone (OR=0.87; 95% CI: 0.71-10.8) and the arid zone (OR=1.27; 95% CI: 1.19-1.36). Increased likelihood of EoE was also associated with increasing odds of being in the cold climate zone. Compared with patients with normal esophageal biopsies, patients with dysphagia, a clinical suspicion of EoE, no reflux or Barrett's esophagus, esophageal eosinophilia, and eosinophilic microabscesses had the highest adjusted odds of being in a cold climate zone (OR 2.02; 1.78-2.28).

Conclusions: Esophageal eosinophilia differs significantly between K-G climate zones, with the highest prevalence in the cold and arid zones. Geographical and climate patterns may help identify candidate antigens characteristic to high-prevalence areas to be targeted for future investigation.