The epidemiology of inflammatory bowel disease: East meets West.

The incidence of inflammatory bowel diseases (IBD) in East has risen over the past decade to become a global disease. Exploring East versus West differences in the epidemiology of IBD could enhance our understanding of the multifactorial nature and heterogeneity of the disease. In this narrative review, we aim to compare the epidemiology of IBD between eastern and western countries by summarizing evidence from population-based cohort studies in the last ten years.A thorough literature search on PubMed was conducted to identify studies reporting population-based data on the epidemiology of IBD. Only studies published within the past ten years were selected. Reference lists from the selected studies were manually searched for further relevant studies.The incidence rate of IBD has increased rapidly in East while plateauing in West. More patients in East present with complicated disease, while disease course is largely comparable between East and West. Some of the genetic and environmental risk factors contributing to IBD exert different effects in East and West which might owe to potential differences in the underlying mechanisms.IBD has become a global disease with the increasing incidence in previously low-prevalent regions in East. However, population-based data from East is still scarce and studies with long durations of follow-up is warranted in the future. Considering the differential effects of genetic and environmental risk factors in East and West, future studies should seek to discover novel genetic and environmental risk factors which might specifically apply to eastern populations.