Effects of smoking on the presentation and clinical course of inflammatory bowel disease

Eur J Gastroenterol Hepatol. 1997 Jul;9(7):683-7. doi: 10.1097/00042737-199707000-00007.


Objective: To evaluate the influence of regular smoking on the presentation and clinical course of inflammatory bowel disease.

Methods: We performed a case-control study interviewing 160 inflammatory bowel disease patients (63 with Crohn's disease (CD) and 97 with ulcerative colitis (UC)) and 140 first-degree relatives as controls. The risk of developing the disease relative to a smoking habit was calculated as the odds ratio. Furthermore, to evaluate the influence of smoking on the subsequent course of inflammatory bowel disease, we performed a multivariate analysis that included pertinent variables such as the need for surgery, number of hospitalizations and relapses.

Results: The pattern of smoking in UC patients was different from that in CD patients. In UC there was a significant predominance of non-smokers and ex-smokers (P = 0.02), whereas smoking habits in CD were not different from those in controls. Giving up smoking was a risk factor to develop UC (odds ratio: 3.2, P = 0.02). In UC, non-smokers and specially ex-smokers need surgery more frequently than smokers (P < 0.01). Otherwise the relapse/year index was not influenced by smoking. In CD there was a non-significant association between smoking habits and the various clinical parameters analysed. UC patients who begin smoking after diagnosis of the disease present a significant reduction in the number of recurrences.

Conclusion: Smoking habit significantly affects the presentation and clinical course of UC, whereas in CD, a smoking habit does not have any apparent influence on the disease.

MeSH terms

  • Adult
  • Case-Control Studies
  • Colitis, Ulcerative / diagnosis*
  • Colitis, Ulcerative / epidemiology
  • Crohn Disease / diagnosis*
  • Crohn Disease / epidemiology
  • Female
  • Humans
  • Male
  • Middle Aged
  • Multivariate Analysis
  • Risk Factors
  • Smoking / adverse effects*
  • Surveys and Questionnaires