Participating centres and characteristics of the cohorts
| Centre and country | Size of cohort | Nature of cohort | No of participants identified with incident ulcerative colitis |
| Norfolk, UK | 25639 | Population-based cohort of men and women aged 45–74 years. Recruited between 1993 and 1997. Cases identified from follow-up questionnaires, in-patient admission data and histopathology records | 25 |
| Heidelberg, Germany | 25540 | Population-based cohort of men aged 45–65 years and women aged 35–65 years. Recruited between 1994 and 1998. Cases identified from follow-up questionnaires | 4 |
| Potsdam, Germany | 27548 | Population-based cohort, men and women, aged 35–64 years. Recruited between 1994 and 1998. Cases identified from follow-up questionnaires | 13 |
| Florence, Italy | 13583 | Population-based cohort, men and women aged 34–64 years. Recruitment between 1993 and 1998. Cases identified from regional databases of inflammatory bowel disease | 8 |
| Umeå, Sweden | 25732 | Population-based cohort, men and women aged 30–60 years. Recruited between 1992 and 1996. Cases identified from regional databases of inflammatory bowel disease | 15 |
| Malmö, Sweden | 28098 | Population based cohort, men and women aged 45–69 years. Recruited between years 1991–1996. Cases identified from regional databases of inflammatory bowel disease | 21 |
| Aarhus and Copenhagen, Denmark | 57053 | Population-based cohort of men and women aged 50–64 years. Recruited between 1993 and 1997. Cases identified from national databases of inflammatory bowel disease | 40 |
| Total | 203193 | 126 |