Esophageal Eosinophilia and Eosinophilic Esophagitis Are Increased in Rural Areas with Low Population Density: Results from a National Pathology Database

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Purpose: Eosinophilic esophagitis (EoE) is an increasingly prevalent chronic disease and is thought to arise from an allergy/immune-mediated process. The relationship between population density, EoE, and esophageal eosinophilia is unknown. Our aim was to estimate the association between EoE and esophageal eosinophilia with population density. Methods: We conducted a cross-sectional study of patients with esophageal biopsies in a U.S. national pathology database between January, 2009 and June, 2012. Using Geographic Information Systems (GIS), the population density (number of individuals per square mile) was determined for each patient zip code. The odds of esophageal eosinophilia and EoE were estimated for each quintile of population density after controlling for age, sex, race and distance traveled for endoscopy. Sensitivity analyses were performed with varying case definitions of EoE. Results: Of 292,621 unique patients in the source population, 91,929 had normal esophageal biopsies and 14,739 had esophageal eosinophilia with ≥15 eosinophils per high-power field (eos/hpf). Those with esophageal eosinophilia were generally younger (45 vs. 54 years), more likely to be male (64% vs 35%) and had more dysphagia (54% vs. 26%) than those with normal biopsies (p<0.05 for all). After multivariate analysis, the odds of esophageal eosinophilia decreased with increasing population density (p for trend < 0.001) (Figure). Compared to those in the lowest quintile of population density, odds of esophageal eosinophilia were significantly reduced amongst those in the highest quintile of population density (OR 0.79; 0.73-0.85). A similar dose-response trend was observed across case definitions of EoE (Figure).FigureConclusion: Population density is strongly and inversely associated with both esophageal eosinophilia and EoE, with these conditions being more common in rural areas. This association persists in sensitivity analyses. Environmental exposures in rural areas may be key in the pathogenesis of EoE. Disclosure - Jensen - nothing to disclose Hoffman - nothing to disclose Shaheen - nothing to disclose Genta - employee of Miraca Research Institute and Miraca Life Sciences where the database used in this study is maintained.