Epidemiological studies of migration and environmental risk factors in the inflammatory bowel diseases Original paper

What was studied?

This article reviews the environmental risk factors and migration patterns related to the increasing incidence of inflammatory bowel diseases (IBD), specifically Crohn’s disease (CD) and ulcerative colitis (UC). The study primarily focuses on epidemiological data, drawing attention to migration patterns that help identify environmental influences contributing to the onset and clinical progression of IBD. It assesses migration cohorts, with particular emphasis on first and second-generation migrants moving from regions with low IBD incidence to areas with higher prevalence, in order to study the environmental triggers involved.

Who was studied?

The study investigates populations from various ethnic backgrounds, especially focusing on first- and second-generation migrants. These cohorts were chosen due to their transition from areas with low IBD incidence to areas with high IBD prevalence, thus providing an excellent opportunity to explore the effects of environmental changes on disease manifestation. The study highlights the epidemiology of IBD in migrant populations from the Middle East, including immigrants to Australia, as a prime example of how migration studies can offer insight into the contribution of environmental factors. Furthermore, the review discusses the differences in disease characteristics between migrants and native populations and between different generations of migrants.

Most important findings

The article presents a comprehensive review of several epidemiological studies that have identified various environmental factors associated with IBD. It found that migration from low-incidence regions to high-incidence regions leads to an increased risk of IBD, especially among second-generation migrants. Studies from countries like the UK, Sweden, and Israel showed a rise in the incidence of IBD among first- and second-generation migrants from regions with historically low IBD rates. Notably, migrants from Middle Eastern countries to developed countries such as Australia were identified as an emerging cohort for further research into IBD’s environmental triggers. Smoking, oral contraceptive use, and childhood infections were identified as significant but controversial environmental factors. Additionally, a shift towards Westernized diets and lifestyles in migrant populations was implicated in the increasing prevalence of IBD, supporting the hygiene hypothesis, which posits that improved hygiene and decreased exposure to infections may increase susceptibility to autoimmune diseases like IBD.

Key implications

The primary implication of this study is the identification of migrant groups, especially those from regions with historically low IBD incidence, as ideal candidates for future epidemiological research. These populations offer a unique opportunity to study the environmental risk factors influencing IBD onset in developed countries. Furthermore, the review underscores the need for studies that compare first- and second-generation migrants to understand how lifestyle and environmental changes influence the development and progression of IBD. This approach could lead to a better understanding of IBD’s pathogenesis and provide insights into how modern lifestyles, including diet and hygiene, contribute to disease manifestation. Additionally, future research should focus on disentangling the genetic and environmental factors involved in IBD to help develop targeted prevention and treatment strategies for at-risk populations.