1 Departments of Epidemiology and Nutrition, Harvard T.H. Chan School of Public Health, 677 Huntington Ave, Kresge 801 A, Boston, MA, 02115, USA. msong@hsph.harvard.edu.
2 Clinical and Translational Epidemiology Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA. msong@hsph.harvard.edu.
3 Division of Gastroenterology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA. msong@hsph.harvard.edu.
4 Institute of Health and Society, University of Oslo, Oslo, Norway.
5 Department of Transplantation Medicine, Oslo University Hospital, Oslo, Norway.