1. Medical Research Council Population Health Research Unit at the University of Oxford, Oxford, UK
2. Clinical Trial Service Unit and Epidemiological Studies Unit (CTSU), Nuffield Department of Population Health, University of Oxford, Oxford, UK
3. National Institute for Health Research, Oxford Biomedical Research Centre, Oxford University Hospital, Oxford, UK
4. Medical Research Council Integrative Epidemiology Unit, University of Bristol, UK
5. Population Health Sciences, University of Bristol, Bristol, UK
6. National Institute for Health Research Bristol Biomedical Research Centre, Bristol, UK