The relationship between heritability and smoking habits in Crohn's disease

OBJECTIVE: In Crohn's disease (CD), the relationship between genetic predis position and smoking has not been well defined. The aim of this study was t o compare the smoking habits at the time of the diagnosis of CD patients ha ving familial occurrence of inflammatory bowel disease (IBD) with those of some control groups. METHODS: In a multicenter study, 136 CD patients with a relative with IBD, 272 healthy controls matched for sex and age, 500 CD patients without famil ial occurrence of IBD, and 84 ulcerative colitis patients (UC) with familia l occurrence of IBD were personally interviewed about their smoking habits. In addition, data for 35 healthy siblings of patients with familial CD wer e collected by interviewing the patients' relatives. RESULTS: The prevalence of smokers was found significantly higher in CD pat ients with a family history for IBD than in healthy controls and in familia l UC patients (OR 2.28 CI 1.5-3.48 and OR 5.81 CI 3.15-10.75, respectively) . No significant difference was found either in the percentage of smokers o r in the number of cigarettes smoked per day between familial and sporadic CD patients. Among all siblings of CD patients, 72% of affected siblings an d 34% of healthy siblings were smokers, concordant with their relatives. CONCLUSIONS: In CD patients with familial occurrence of IBD, the percentage of smokers is elevated. It is possible that in a genetically predisposed p opulation, smoking could be an important environmental factor in determinin g CD or expressing this disease instead of UC, (C) 2000 by Am. Cell. of Gas troenterology).