OBJECTIVES: Crohn's disease (CD) can be classified by site of involvement and by clinical behavior. Claims for stability of behavior are based on patients who have had surgery, usually within 8 yr of diagnosis. Disease during this period may begin as inflammatory and may evolve into stricturing or fistulizing behavior. Our aim was to determine the influence of genetic and environmental factors on the prevalence of inflammatory behavior among patients who have had CD for < 8 yr. METHODS: Disease type (inflammatory, stricturing, or fistulizing), site, and duration were determined in 311 consecutive patients with CD. The analysis was then restricted to those with a disease duration of <8 yr, and influences on the prevalence of inflammatory type disease were compared with those of the complicated type (fistulizing and stricturing), including disease site, family history, Jewish ethnicity, and pack-years of cigarette smoking after diagnosis were determined through univariate and multivariate analyses. RESULTS: The prevalence of inflammatory type disease was 0.63 and 0.3 (p < 0.0001) in patients with a disease duration of <8 yr and ≥8 yr, respectively. Multivariate analysis revealed a 91% decrease in the odds of inflammatory disease among those with ≥1 pack-year of smoking after diagnosis among individuals with disease <8 yr. This was not influenced by disease location, family history of inflammatory bowel disease (IBD), or Jewish ethnicity. CONCLUSIONS: The prevalence of inflammatory CD decreased with time. Tobacco consumption was associated with this decline during the early phase of disease, suggesting that tobacco may influence the progression of inflammatory to stricturing or fistulizing type disease.
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