1. McMaster University; Department of Medicine, Division of Gastroenterology; 1200 Main Street West Room 4W8E Hamilton Ontario Canada L8N 3Z5
2. The General Infirmary at Leeds; Gastroenterology Unit, Centre for Digestive Diseases; Great George Street Leeds UK LS1 3EX
3. University of Birmingham; Public Health, Epidemiology and Biostatistics; Edgbaston Birmingham UK B15 2TT
4. King's College London; Division of Health and Social Care Research; 7th Floor Capital House 42 Weston Street London UK SE1 3QD
5. The University of Birmingham; Department of Primary Care and General Practice; The Medical School Edgbaston Birmingham UK B15 2TT
6. International Agency for Research on Cancer; 150 cours Albert-Thomas Lyon France 69372