[Epidemiological study on the incidence of inflammatory bowel disease in 4 Spanish areas. Spanish Group on the Epidemiological Study of Inflammatory Bowel Disease]

The incidence of inflammatory bowel disease (IBD) shows marked geographical variations. The aim of this study was to determine and compare the incidence of IBD in four Spanish areas: Sabadell (Northeast), Vigo (Northwest), Mallorca island and Motril (South).Prospective survey based on inception cohorts over a two-years period (1 October 1991 to September 1993). Subjects were the patients resident in these areas and diagnosed of IBD according to a standard protocol for case ascertainment and definition.Altogether 328 cases were identified, of whom 191 were diagnosed as ulcerative colitis (UC), 135 as Crohn's disease (CD) and 2 as indeterminate colitis. The overall adjusted incidence rate per 100,000 persons between ages 15-64 years of UC and CD were respectively 9.8 and 5.2 in Sabadell, 7.7 and 5.0 in Vigo, 7.8 and 5.8 in Mallorca and 4.3 and 6.5 in Motril. The Incidence rate ratio showed no significant differences for either conditions among these areas. The global adjusted incidence rate of UC in Spanish areas (8.0; IC 95%: 6.3-9.7) was significantly lower to that of Northern European countries while that of CD (5.5; IC 95%: 4.1-6.9) was between that of Northern and Southern Europe with no significant differences.The incidence of IBD did not show differences among the Spanish areas, and rates are between 2 and 6 times higher than those previously reported. The incidence of UC is significantly lower than that observed in the North of Europe, while for CD the incidence is between that of Northern and Southern Europe.