London School of Hygiene & Tropical Medicine - MRC International Statistics & Epidemiology Group, National Institute of Medical Research, Biomedical Research and Training Institute, Biomedical Research and Training Institute, London School of Hygiene & Tropical Medicine - MRC Tropical Epidemiology Group (TEG), London School of Hygiene & Tropical Medicine - Department of Clinical Research, London School of Hygiene & Tropical Medicine - MRC International Statistics & Epidemiology Group, Stellenbosch University - Institute for Life Course Health Research, London School of Hygiene & Tropical Medicine - Department of Non-Communicable Disease Epidemiology, London School of Hygiene & Tropical Medicine - MRC International Statistics & Epidemiology Group, University of New South Wales (UNSW) - School of Population Health, London School of Hygiene & Tropical Medicine - Department of Clinical Research and London School of Hygiene & Tropical Medicine - Department of Clinical Research