Lack of association between smoking and inflammatory bowel disease in Jewish patients in Israel

Background/Aims: An excess of smokers in patients with Crohn's disease (CD) and a paucity of smokers in patients with ulcerative colitis (UC) were reported in many studies. The aim of this study was to examine the association between smoking and inflammatory bowel disease (IBD) in Israel. Methods: Two independent studies were performed. Patients with recent IBD in comparison with matched population and outpatient controls and patients with chronic UC and CD were studied. Altogether, 475 subjects were investigated. Results: In both studies, the presence of current smokers was lower in CD (9% and 18%) than in UC (24% and 26%). The proportions of nonsmokers in both studies were similar (UC, 61% and 65%; CD, 67% and 70%) and comparable to those found in their two control groups (57% and 61%; 63% and 68%, respectively) and to the general population of Israel. All differences in smoking habits between patient groups and their controls were not statistically significant, except for the paucity of current smokers in the small group of patients with newly diagnosed CD (P < 0.05). A matched analysis produced similar results. Conclusions: The expected associations between smoking and IBD could not be confirmed. Two hypotheses are considered: (1) the association between smoking and IBD may not be universal, and (2) our findings may be related to the higher genetic predisposition to IBD in Jewish people.