1. Department of Gastroenterology; Faculty of Medicine and Health; Örebro University; Örebro Sweden
2. Clinical Epidemiology and Biostatistics; School of Medical Sciences; Örebro University; Örebro Sweden
3. Unit of Biostatistics; Institute of Environmental Medicine; Karolinska Institutet; Stockholm Sweden
4. Department of Medical Sciences; Gastroenterology Research Group; Uppsala University; Uppsala Sweden