Incidence of juvenile-onset Crohn's disease in Scotland: Association with northern latitude and affluence

Background & Aims: The incidence of Crohn's disease in Scottish children has increased steadily over 30 years. Many studies have investigated genetic influence or possible links with childhood events. We aimed to study sociodemographic and/or geographic distribution of juvenile=onset Crohn's disease in Scotland. Methods: Using a previously established and validated database covering the entire Scottish population, 580 Scottish children (<16 years of age at symptom onset) with inflammatory bowel disease incident between 1981 and 1995 were identified. Postcodes of incident cases were classed for geographic location and material deprivation. Incidence rates (/100,000/year) were sex standardized to the 1991 census population. The effects of sex, geographic location, time, and deprivation category were estimated from a multifactorial Poisson regression model. Results: The incidence of juvenile-onset Crohn's disease was 2.3 (95% CI: 2.0-2.5) for the time period 1981 to 1995 and was significantly higher in northern (3.1, 95% CI: 2.6-3.8) than in southern Scotland (2.1, 95% CI: 1.9-2.4, P<0.001). The incidence of juvenile-onset ulcerative colitis did not show north/south variation (P = 0.677). The relative risks of developing CD were significantly lower in postcode areas with deprivation categories 2-7 as compared with deprivation score 1 (most affluent, P = 0.033). This pattern was not seen for UC. Conclusions: There was an increased incidence of juvenile-onset Crohn's disease in northern compared with southern Scotland. Children from more affluent areas had a higher relative risk of developing Crohn's disease. Juvenile onset ulcerative colitis did not show north/south variation in incidence or association with affluence.