ORIGINAL ARTICLE The effect of smoking after surgery for Crohn’ s disease: a meta-analysis of observational studies George E. Reese & Theodore Nanidis & Catherine Borysiewicz & Takayuki Yamamoto & Timothy Orchard & Paris P. Tekkis Accepted: 16 July 2008 / Published online: 2 September 2008 # Springer-Verlag 2008 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. Design Meta-analysis of observational studies. Data sources Medline, Embase, Ovid and the Cochrane database. Materials and methods A literature search was performed to identify studies published between 1966 and 2007 com- paring outcomes of smokers, ex-smokers and non-smokers with Crohn’ s disease. Random-effect meta-analytical tech- niques 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 encour- aged to stop smoking since the risk of disease relapse is minimised upon its cessation. Keywords Crohn’ s disease . Smoking . Surgery . Meta-analysis Introduction Treating illness caused by smoking is estimated to cost the National Health Service up to £1.7 billion every year in terms of general practitioner visits, prescriptions, treatment and operations [1]. The association between smoking and inflammatory bowel disease was first noted in the early 1980s [2, 3] when it was observed that smokers were under-represented in populations of patients with ulcerative colitis and over-represented in Crohn’ s disease. In a recent review of factors affecting recurrence of Crohn’ s disease, the most important environmental factor was noted to be Int J Colorectal Dis (2008) 23:1213–1221 DOI 10.1007/s00384-008-0542-9 George E. Reese and Theodore Nanidis with equal contribution. G. E. Reese : T. Nanidis : C. Borysiewicz : P. P. Tekkis (*) Department of Biosurgery and Surgical Technology, Imperial College London, St Mary’ s Hospital, 10th Floor QEQM Building, Praed Street, London W2 1NY, UK e-mail: p.tekkis@imperial.ac.uk T. Yamamoto Inflammatory Bowel Disease Centre, Yokkaichi Social Insurance Hospital, Yokkaichi, Mie, Japan T. Orchard Department of Medicine, Imperial College London, St Mary’ s Hospital, London, UK