1. Upper Gastrointestinal Surgery, Department of Molecular Medicine and Surgery; Karolinska Institutet; Stockholm Sweden
2. Section of Gastrointestinal Cancer, Division of Cancer Studies, King's College London; London United Kingdom
3. Stockholm University Demography Unit, Department of Sociology; Stockholm University; Stockholm Sweden
4. Unit of Epidemiology, Institute of Environmental Medicine, Karolinska Institutet; Stockholm Sweden
5. Swedish Institute for Social Research; Stockholm University; Stockholm Sweden