Epidemiology

• frequently seen in industrialized countries (in Europe and North America) and is rare in underdeveloped countries (1)
  
  
• even in countries with several ethnic groups, the risk of developing the disease was lower in those with a less westernised way of life (1)
  
  
• Crohn's & Colitis UK estimate there are at least 115,000 people in the UK with Crohn's disease (3)
  
  
• annual incidence in the UK is approximately 5/100,000. A GP in UK can expect a new case of Crohn’s disease every seven years (4)
  
  
• women more affected than men
  
  
• most commonly affected age group is between 15 and 30 years, although it may be seen in people of any age (4). There is also a second peak in the elderly.
• at the time of diagnosis
  • 15% of people are older than 60 years
  • 20-30% are younger than 20 years (4)
    
    
• familial clustering and involves ulcerative colitis as well as Crohn's disease
  
  
• more common in smokers than non-smokers (4:1)
  
  
• most common site of disease is the terminal ileum
  

Reference:

• (1) Malekzadeh F et al. Crohn's disease and early exposure to domestic refrigeration. PLoS One. 2009;4(1):e4288
• (2) Cummings JR, Keshav S, Travis SP. Medical management of Crohn's disease. BMJ. 2008;336(7652):1062-6
• (3) NICE (May 2019). Crohn's disease: management
• (4) National Institute for Health and Clinical Excellence (NICE) 2010. Infliximab (review) and adalimumab for the treatment of Crohn’s disease