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Epidemiology of inflammatory bowel disease

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

Authoring team

Ulcerative colitis has an incidence of 5 to 8 people per 100,000 in Northern Europe and North America. Crohn's disease has an incidence of 5 per 100,000. Variations are seen with:

  • race - in the USA, white people are 3 times more susceptible to UC, and 5 times more susceptible to Crohn's, than are Afro-Caribbean people

  • sex - approximately the same

  • age - peaks between 20 and 30 and between 50 and 60 years

  • geography:
    • common in developed communities of N. America, S. Africa, Australasia and W. Europe
    • less common in Japan and S. and E. Europe
    • rare in rest of Asia, Africa and S. America

  • genetics:
    • monozygotic concordance in Crohn's
    • HLA-DR2 is associated with a ANCA positive form of UC
    • familial aggregations.
    • increased incidence of HLA-B27 in patients with IBD and ankylosing spondylitis.
    • greater prevalence in Ashkenazi Jews

  • smoking:
    • Crohn's is 3-4x more common in smokers than non-smokers
    • ulcerative colitis is uncommon in smokers
    • there seems to be a dose-response relationship between smoking and IBD

  • oral contraceptive pill may predispose to development of Crohn's to some extent, although it may just predict other behaviours

  • atopy more common among patients and there is an association with coeliac disease among relatives

  • appendicectomy is more common in non-IBD sufferers, and so may have a protective effect


  • Prescriber 2001; 12 (20): 43-58
  • Shanahan F. Pathogenesis of Ulcerative Colitis. Lancet 1993; 342: 407-11
  • Mayberry JF et al. Ulcerative colitis. Medicine International 1994; 22(8):314-20.
  • Lunney PC, Leong RW. Review article: Ulcerative colitis, smoking and nicotine therapy. Aliment Pharmacol Ther. 2012;36:997-1008

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