The effect of smoking after surgery for Crohn's disease: a meta-analysis of observational studies

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. Meta-analysis of observational studies. Medline, Embase, Ovid and the Cochrane database. 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. 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). 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.