Epidemiology of inflammatory bowel disease

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

Reference:

• 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