Inflammatory bowel diseases in Faroese‐born Danish residents and their offspring: further evidence of the dominant role of environmental factors in IBD development

• Published in: Alimentary Pharmacology & Therapeutics
• Main Authors: Hammer, T., Lophaven, S. N., Nielsen, K. R., von Euler‐Chelpin, M., Weihe, P., Munkholm, P., Burisch, J., Lynge, E.
• Other Authors: Faroese Research Council, European Crohn's and Colitis Organisation (ECCO), Beckett Foundation, The Danish Colitis-Crohn Patients Organisation (CCF), Aage and Johanne Louis-Hansen Foundation
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2017
• Subjects: Faroe Islands
• Online Access: http://dx.doi.org/10.1111/apt.13975; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fapt.13975; https://onlinelibrary.wiley.com/doi/pdf/10.1111/apt.13975

Summary Background The incidence of inflammatory bowel disease ( IBD ) is record high in the Faroe Islands, and many Faroese emigrate to Denmark, where the IBD incidence is considerably lower. Aim To study the IBD incidence in first‐, second‐ and third‐generation immigrants from the Faroe Islands to Denmark to assess the extent to which the immigrants adopt the lower IBD incidence of their new home country. Methods Data on Faroese‐born Danish residents and their children were retrieved from the Danish Central Population Register for 1980–2014. Incident IBD cases were identified from the Danish National Patient Register. Standardised Incidence Ratios ( SIR s) were used to compare the IBD risk in immigrants with that of Danes. 95% confidence intervals ( CI ) were calculated using the square‐root transform. Results First‐generation Faroese immigrants had a higher IBD incidence than Danes, SIR 1.25 (95% CI , 0.97–1.59) for men and 1.28 (95% CI , 1.05–1.53) for women. This excess risk derived from ulcerative colitis ( UC ), SIR 1.44 (95% CI , 1.10–1.87) for men and 1.36 (95% CI , 1.09–1.68) for women. No excess risk was found for Crohn's disease ( CD ). The UC risk was nearly doubled during the immigrants’ first 10 years in Denmark; SIR 2.13 (95% CI , 1.52–2.92) for men and 1.63 (95% CI , 1.19–2.18) for women. Conclusions Although some impact of genetic dilution cannot be excluded, our findings indicate importance of gene‐environment interplay in UC , as the excess UC risk in Faroese immigrants to Denmark disappeared over time and over one generation in men and over two generations in women.