Aspirin in the aetiology of Crohn's disease and ulcerative colitis: a European prospective cohort study.

Background: Aspirin has detrimental effects on the gastrointestinal tract mucosa and may play a role in the aetiology of inflammatory bowel disease.

Aim: To investigate if the regular use of aspirin is associated with the development of Crohn's disease (CD) and ulcerative colitis (UC) using, for the first time, a prospective cohort study design.

Methods: A total of 135,780 men and women in Europe, aged 30-74years, were recruited into the European Prospective Investigation into Cancer and Nutrition study. Participants completed questionnaires at baseline detailing their regular aspirin use and were then followed up to identify those who developed either incident CD or UC. Each case was matched with four controls and odds ratios (OR) were calculated, adjusting for cigarette smoking. Potential interactions between aspirin and smoking were assessed.

Results: A total of 35 participants developed CD and a further 84 were diagnosed with UC. Regular aspirin intake was positively associated with the risk of developing CD (OR=6.14, 95% CI=1.76-21.35). In those who took aspirin and smoked there was no detectable increased risk of CD (OR=0.30, 95% CI=0.03-3.08). No association was found between regular aspirin use and UC (OR=1.29, 95% CI=0.67-2.46).

Conclusions: A strong positive association between regular aspirin use and CD, but not UC, was observed. The data suggest that regular aspirin use should be measured in epidemiological work on CD. If such findings are consistent in other work then aspirin may affect the development of CD in a middle-aged to elderly population.