Latitude and Celiac Disease Prevalence: A Meta-Analysis and Meta-Regression

Background & Aims: The latitudinal gradient effect is described for several autoimmune diseases including celiac disease in the United States. However, the association between latitude and global celiac disease prevalence is unknown. We aimed to explore the association between latitude and serology-based celiac disease prevalence through meta-analysis. Methods: We searched MEDLINE, Embase, Cochrane, and Scopus databases from their beginning through June 29, 2018, to identify screening studies that targeted a general population sample, used serology-based screening tests, and provided a clear location from which we could assign a latitude. Studies were excluded if sampling was based on symptoms, risk factors, or referral. Study selection and data extraction were performed by independent reviewers. The association measures between latitude and prevalence of serology-based celiac disease were evaluated with random-effects meta-analyses and meta-regression. Results: Of the identified 4667 unique citations, 128 studies were included, with 155 prevalence estimates representing 40 countries. Celiac disease was more prevalent at the higher latitudes of 51° to 60° (relative risk [RR], 1.62; 95% CI, 1.09–2.38) and 61° to 70° (RR, 2.30; 95% CI, 1.36–3.89) compared with the 41° to 50° reference level. No statistically significant difference was observed at lower latitudes. When latitude was treated as continuous, we found a statistically significant association between CD prevalence and latitude overall in the world (RR, 1.03, 95% CI, 1.01–1.05) and a subregional analysis of Europe (RR, 1.05; 95% CI, 1.02–1.07) and North America (RR, 1.1; 95% CI, 1.0–1.2). Conclusions: In this comprehensive review of screening studies, we found that a higher latitude was associated with greater serology-based celiac disease prevalence.