1 Clinical Trial Service Unit & Epidemiological Studies Unit and MRC Population Health Research Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK. Electronic address: rory.collins@ndph.ox.ac.uk.
2 Clinical Trial Service Unit & Epidemiological Studies Unit and MRC Population Health Research Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK.
3 MRC Integrative Epidemiology Unit, University of Bristol, Bristol, UK.
4 Department of Non-Communicable Disease Epidemiology, London School of Hygiene & Tropical Medicine, University of London, London, UK.