A Higher Incidence of Isolated Biliary Atresia in Rural Areas: Results from an Epidemiological Study in The Netherlands

OBJECTIVES: Environmental factors may be involved in the pathogenesis of biliary atresia (BA). This epidemiological study aimed to analyse the relationships between the incidence of BA, the incidence of confirmed viral or bacterial infections and population density, as well as geographical and temporal clustering of BA in the Netherlands.

STUDY DESIGN: Correlations between the monthly incidence of BA and the number of confirmed infections were assessed. BA incidence per province was calculated and compared to the province with highest population density. Birthplaces were classified as rural or urban. Temporal clustering of month of birth and month of conception were analysed. We performed analyses for isolated BA (IBA) and syndromic BA (SBA) separately. Chi, logistic regression and Walter & Elwood test were used.

RESULTS: 262 IBA and 49 SBA patients, born between 1987-2018, were included. IBA incidence correlated to the number of confirmed infections of e.g. C. Trachomatis (R = 0.14;P = 0.02) and Adenovirus (R = 0.22;P = 0.005). We observed a higher incidence of IBA (0.75/10,000;OR = 1.86;P = 0.04) and SBA (0.27/10,000;OR = 6.91;P = 0.001) in Groningen and a higher incidence of SBA in Gelderland (0.13/10,000;OR = 3.35;P = 0.03). IBA incidence was 68% higher in rural (0.67/10,000) vs. urban areas (0.40/10,000) (P = 0.02). The estimated month of conception of patients with SBA clustered in November (85% increase compared to average SBA incidence [0.09/10,000;P = 0.04]).

CONCLUSIONS: IBA incidence correlated weakly with national confirmed infections. IBA and SBA incidence varied geographically in the Netherlands. IBA incidence was higher in rural than in urban areas, which may be explained decreased exposure to pathogens. Our results provide support for a role of environmental factors in the pathogenesis of IBA.