Inflammatory Bowel Disease in Migrant Populations: Should we Look Even Further Back?

BACKGROUND: The incidence of inflammatory bowel disease (IBD) continues to rise worldwide. Despite the advances in pharmacotherapy, the etiopathogenesis of Crohn's disease (CD) and ulcerative colitis (UC) remains underexplained. The migratory waves are a challenging setting to analyze the evolution of IBD prevalence and to infer its triggering factors. OBJECTIVE: Our study aimed to overview the literature regarding IBD prevalence and phenotype in first- and second-generation migrants Also, we aimed to summarize the migration history and to draw a possible correlation with IBD distribution. METHODS: A non-systematic review was performed following electronic (PubMed and Web of Science) and manual searches on relevant topics. RESULTS: Overall, first-generation migrants tend to maintain the IBD risk of the native country. On the following generation, the risk tends to converge to that of the destination country. Earlier age at migration modulates IBD risk, suggesting that the degree of exposure to environmental and socio-economic factors can be decisive for disease progression. In general, CD needs more time to reach a disease burden similar to that of the host country, indicating that UC may be more affected by nongenetic factors and genetic-nongenetic interactions. CONCLUSION: IBD phenotypes and natural history vary in migrants and according to ethnicity; however, the trends are not consensual among cohorts. Further studies are warranted to analyze the effect of genetic background and environmental risk factors in different ethnic groups, providing evidence to move towards the identification of at-risk individuals, prevention, and earlier diagnosis of IBD.