1. Medical Sciences Division, University of Oxford, Oxford OX2 6HG, UK
2. Oxford University Clinical Academic Graduate School, Oxford OX3 9DU, UK
3. Senior Medical Registrar, Oxford Deanery, Oxford OX3 9DU, UK
4. Department of Upper GI Surgery, Oxford University Hospitals, Oxford OX3 7LE, UK
5. Nuffield Department of Surgical Sciences, Oxford OX3 9DU, UK
6. Department of Cardiovascular Medicine, University of Oxford, Oxford OX2 6HG, UK
7. Director of MedicineAfrica, Oxford OX4 1JE, UK
8. Fulbright Scholar, Harvard School of Public Health, Boston, MA 02115, USA