Incidence of celiac disease among second-generation immigrants and adoptees from abroad in Sweden: evidence for ethnic differences in susceptibility

Abstract

Background and aims. The incidence of celiac disease (CD) shows large, worldwide variation. However, whether its causes are environmental (gluten-containing diet) or genetic (specific haplotype) have not been established. The aim of the present study is to examine the incidence of CD among second-generation immigrants and adoptees from abroad to disentangle genetic/ethnic versus environmental influences (assuming that immigrants have similar gluten exposures to native Swedes, and thus differ from them only in terms of their genetic background). Methods. Second-generation immigrants and adoptees from abroad were identified in the MigMed 2 Database and were followed until diagnosis of CD, death, or the end of study. Standardized incidence ratios (SIRs) were calculated among these immigrants with native Swedes as the reference group. Results. A total of 1,050,569 children were defined as second-generation immigrants and the overall SIR of CD (SIR = 0.89, 95% confidence interval 0.84–0.94) was significantly lower than that of native Swedes. The incidence of CD among children with parents from Western, Eastern, and Northern European countries was similar to that in native Swedes, but was lower for those with parents from low-prevalence countries, especially Eastern and Southeast Asian countries. A total of 51,557 children born in foreign countries were adopted by Swedes. Adoptees from Eastern Asia had a significantly decreased SIR of CD. Conclusions. The decreased incidence of CD in second-generation immigrants and some groups of adoptees from abroad strongly suggests that ethnic genetic heterogeneity may contribute to the worldwide variation in CD incidence.

Key Words::

• Adoptee
• celiac disease
• ethnic
• follow-up
• incidence
• risk factors
• Sweden

Acknowledgements

This work was supported by the Swedish Research Council, the Swedish Council for Working Life and Social Research and the Swedish Research Council Formas.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.