Lack of association between smoking and Crohn’s disease but the usual association with ulcerative colitis in Jewish patients in Israel: a multicenter study

Abstract

OBJECTIVE: The association between smoking and inflammatory bowel disease (IBD) is well established, but data in Jewish patients in Israel were discrepant. The aim of this study was to examine the smoking habits of Jewish IBD patients in Israel in a large scale, multicenter study. METHODS: Patients with established IBD aged 18–70 yr were interviewed in relation to smoking and other habits. Two controls (one clinic and one neighborhood control matched by age, sex, community group, and education) were sought for each subject. RESULTS: A total of 534 patients (273 ulcerative colitis [UC], and 261 Crohn’s disease [CD]), along with 478 clinic controls and 430 neighborhood controls, were interviewed. There was no significant difference in the smoking habits between CD patients and their controls. Of patients with CD, 24.5% were current smokers, as compared to 19.9% of clinic controls and 25.2% of neighborhood controls (NS).The odds ratio for CD in current smokers was 1.30 (95% confidence interval 0.85–1.99) versus clinic controls, and 0.96 (0.63–1.46) versus neighborhood controls. There were also no significant differences in the proportion of ex-smokers between the groups. Only12.9% of UC patients were current smokers versus 21.9. % Clinic controls, and 26.4% community controls ( p < 0.005). The proportions of ex-smokers were higher in UC patients 29.7% versus 25.9%, and 19.5% in their respective controls ( p < 0.001 vs community controls). No significant differences were found in the proportions of never-smokers between IBD patients and controls. All the above trends were similar in four different parts of the country. The proportion of current smokers in UC decreased with the extent of disease (19.7% in proctitis, 13.6% in left-sided, and 4.5% in total colitis) ( p < 0.05). Patients with UC were more likely to be light smokers(1–10 cigarettes/day), whereas patients with CD were more likely to be moderate smokers (11–20 cigarettes/day) in comparison to their controls. CONCLUSIONS: The lack of association between smoking and CD has now been established in Jewish patients in Israel. The association was found in UC. The stronger genetic tendency in CD may contribute to this discrepancy.