title: The effect of smoking after surgery for Crohn's disease: a meta-analysis of observational studies.
abstract: OBJECTIVE
  The aim of the study was to quantify the risk of disease recurrence associated with cigarette smoking for individuals with Crohn's disease after disease-modifying surgery.
  
  
  METHODS
  Meta-analysis of observational studies.
  
  
  METHODS
  Medline, Embase, Ovid and the Cochrane database.
  
  
  METHODS
  A literature search was performed to identify studies published between 1966 and 2007 comparing outcomes of smokers, ex-smokers and non-smokers with Crohn's disease. Random-effect meta-analytical techniques were employed to assess the risk of medical or surgical recurrence.
  
  
  RESULTS
  Sixteen studies encompassing 2,962 patients including 1,425 non-smokers (48.1%), 1,393 smokers (47.0%) and 137 ex-smokers (4.6%) were included. Smokers had significantly higher clinical post-operative recurrence than non-smokers (odds ratio [OR] = 2.15; 95%CI = 1.42, 3.27; p < 0.001). Smokers were also more likely to experience surgical recurrence by 5 (OR = 1.06; 95%CI = 0.32; 3.53, p = 0.04) and 10 years of follow-up (OR = 2.56; 95%CI = 1.79, 3.67; p < 0.001) compared to non-smokers, although the crude re-operation rate was not statistically significant. When matched for operation and disease site, smokers had significantly higher re-operation rates to non-smokers (OR = 2.3; 95%CI = 1.29, 4.08; p = 0.005). There was no significant difference between ex-smokers and non-smokers in re-operation rate at 10 years (OR = 0.30; 95%CI = 0.09, 1.07; p = 0.10) or in post-operative acute relapses (OR = 1.54; 95%CI = 0.78, 3.02; p = 0.21).
  
  
  CONCLUSIONS
  Patients with Crohn's disease who smoke have a 2.5-fold increased risk of surgical recurrence and a twofold risk of clinical recurrence compared to non-smokers. Patients with Crohn's disease should be encouraged to stop smoking since the risk of disease relapse is minimised upon its cessation.
authors.affiliation: Department of Biosurgery and Surgical Technology, Imperial College London, St Mary's Hospital, London, W2 1NY, UK.
authors.forename: George E
authors.initials: GE
authors.lastname: Reese
authors.forename: Theodore
authors.initials: T
authors.lastname: Nanidis
authors.forename: Catherine
authors.initials: C
authors.lastname: Borysiewicz
authors.forename: Takayuki
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Timothy
authors.initials: T
authors.lastname: Orchard
authors.forename: Paris P
authors.initials: PP
authors.lastname: Tekkis