Epidemiology and risk factors for IBD

Crohn's disease and ulcerative colitis are complex immunologically mediated diseases that arise due to a dysregulated immune response to commensal flora in a genetically susceptible hostThe incidence of IBD has traditionally been highest in North America and Western Europe with many cohorts suggesting a substantial secular increase over the second half of the twentieth centuryHowever, incidence of IBD is increasing in emerging populations such as Asia, suggesting that changing environmental factors play an important partSmoking and appendectomy were initially described to increase the risk of Crohn's disease and confer protection from ulcerative colitis; however, this relationship seems more complex and could be mediated by geneticsDiet, lifestyle and behaviour, as well as perturbations of the gut microbiota through use of antibiotics, might also have important roles in disease pathogenesisModification of IBD risk factors offer avenues of intervention for disease prevention and improvement of natural history