Long-term clinical outcomes of urban versus rural environment in Korean patients with Crohn's disease: Results from the CONNECT study

Background aims: Environmental factors and genetic predisposition are thought to play important roles in the pathogenesis of Crohn's disease [CD]. Although numerous studies have reported the positive association between urban environment and CD development, few studies have compared the clinical outcomes between urban and rural environments. Therefore, this study aimed to compare the clinical characteristics and long-term prognosis between urban and rural populations of patients with CD. Methods: This retrospective multicenter cohort study included 1 002 Korean patients diagnosed with CD [743 urban residents and 259 rural residents] between 1982 and 2008 from 32 medical centers. The clinical outcomes of urban versus rural populations were compared using the KaplanMeier method and log-rank test. Results: Disease distribution and behavior of the urban population did not differ from those of the rural population. There were no significant differences in the cumulative probabilities of perianal fistula [P = 0.086] and intestinal complications such as stricture [P = 0.109], fistula [P = 0.952], abscess [P = 0.227], and perforation [P = 0.382] between the two groups. In addition, no significant differences were observed between the two groups with regard to the cumulative probabilities of immunosuppressant use [P = 0.527] and biologic agent use [P = 0.731]. Although the cumulative probability of surgery in the urban population was significantly higher than that in the rural population [P = 0.040], this difference was mainly established within the first year from diagnosis [19.1% vs 13.5%, P = 0.042] and observed only among patients diagnosed in 2005-2008 [P = 0.033]. Conclusions: There were no differences in terms of disease presentation and natural history between urban and rural populations, except for a higher rate of surgery in the urban population who were recently diagnosed with CD.