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P688 Is smoking cessation linked to new ulcerative colitis cases?—A retrospective cohort based hypothesis

M. Grueber*1, N. Fournier2, L. Biedermann3, S. Vavricka4, A. Schöpfer5, C. Clair Willi6, M. Allez7, A. J. Macpherson8, P. Juillerat9

1Inselspital, Bern, Department of Gastroenterology, Bern, Switzerland, 2CHUV, Statistics, Lausanne, Switzerland, 3Universitätsspital, Gastroenterology, Zürich, Switzerland, 4Stadtspital Triemli, Gastroenterology, Zürich, Switzerland, 5CHUV, Gastroenterology, Lausanne, Switzerland, 6CHUV, PMU, Lausanne, Switzerland, 7Hôpital Saint-Louis, Gastroenterology, Lausanne, France, 8Inselpital, Gastroenterology, Bern, Switzerland, 9Inselspital, Gastroenterology, Bern, Switzerland


Smoking has differential effect on inflammatory bowel diseases (IBD) deleterious for Crohn’s disease (CD) and protective for ulcerative colitis (UC). Thickness of the mucus layer, immune system (cytokines production), microvasculature, and intestinal microbiome are potential mechanistical factors influenced by the nicotine and numerous other substances. Therefore, it has been hypothesised that smoking cessation is associated with the second peak of diagnosis in UC patients after age 50 (critical age for smoking cessation).1 Our aim was to confirm this hypothesis using data on smoking status at IBD diagnosis.


Adult IBD patients included in the Swiss IBD cohort from November 2006 to November 2015 were asked about their smoking status at diagnosis (using a questionnaire). We compared proportion of former smokers in 10-year groups of UC and CD patients.


In the study, 3 410 IBD patients were initially included in the study; 1 049 patients were excluded because they paediatric patients, had an unknown diagnosis date, provided a lack of information concerning smoking status at diagnosis, or were IC patients. In the end, 2 361 IBD patients (1 366 CD; 995 UC) were included in the analysis. Amongst them, 52% of CD and 24% of UC patients were smokers at diagnosis (proportion of smokers in Switzerland in 2014 29%).

Table 1 Prevalence of current, former, and non-smokers based on diagnosis and gender in the Swiss IBD cohort. Graph 1 shows the proportion of previous smokers for every 10 years of age bracket amongst UC and CD patients. The higher proportion (66 %) of former smokers at diagnosis was in the 50- to 60-year-old group of UC patients compared with only 26% in CD patients between 40 to 50 years (p < 0.001). On a gender basis, the higher proportion of former smokers is particularly and significantly highest amongst males 50–60 yr with UC (68%) and persisting amongst males over 60 yr (52%).

% of all patients at IBD 
diagnosisSmokersNever smokedFormer smokers
CD704 (51.5%)525137 (10%)
UC239 (24%)491265 (26.7%)


The proportion of former smokers at diagnosis increases dramatically and significantly over years in UC patients compared with CD patients. A peak was reached over age 50 years, suggesting an indirect effect of smoking cessation on the second peak of diagnosis in UC.


[1] Takashi H, Matsui T, Hisabe T, et al. Second peak in the distribution of age at onset of ulcerative colitis in relation to smoking cessation. J Gastroenterol Hepatol 2014;29(8):1603–08.