title: Effects of smoking on the presentation and clinical course of inflammatory bowel disease.
abstract: 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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Digestive System Research Unit, Hospital General Vall d'Hebron, Barcelona, Spain.
authors.forename: X F
authors.initials: XF
authors.lastname: Fraga
authors.forename: M
authors.initials: M
authors.lastname: Vergara
authors.forename: C
authors.initials: C
authors.lastname: Medina
authors.forename: F
authors.initials: F
authors.lastname: Casellas
authors.forename: B
authors.initials: B
authors.lastname: Bermejo
authors.forename: J R
authors.initials: JR
authors.lastname: Malagelada
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D003093:Colitis, Ulcerative / Q000175:diagnosis* / Q000453:epidemiology; D003424:Crohn Disease / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects*; D011795:Surveys and Questionnaires