1. Cancer Epidemiology Research Group, Centre for Public Health, Queen's University Belfast; Belfast Northern Ireland
2. Division of Cancer Epidemiology and Genetics; National Cancer Institute, NIH, DHHS; Bethesda MD
3. Department of Gastroenterology; Royal Victoria Hospital, Belfast Health & Social Care Trust; Belfast Northern Ireland
4. Centre of Excellence for Public Health (NI), Centre for Public Health, Queen's University Belfast; Belfast Northern Ireland