1. Departments of Medicine, Division of Gastroenterology, Schulich School of Medicine & Dentistry, Western University, London, ON N6A 5C1, Canada
2. Gastroenterology, Department of Public Health, University Federico II of Naples, 80131 Naples, Italy
3. Division of Epidemiology and Biostatistics, Western University, London, ON N6A 5C1, Canada
4. Lawson Health Research Institute, London, ON N6A 3K7, Canada