Sonia Friedman1, Bente Mertz Nørgård1. 1. Division of Gastroenterology, Hepatology, and Endoscopy, Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts; Center for Clinical Epidemiology, Odense University Hospital, Odense, Denmark; Research Unit of Clinical Epidemiology, Department of Clinical Research, University of Southern Denmark, Odense, Denmark.