1 Clinical Trial Service Unit & Epidemiological Studies Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK.
2 University of Glasgow, Glasgow, UK.
3 Department of Neurology, Cedars-Sinai, Los Angeles, CA, USA.
4 Clinical Trial Service Unit & Epidemiological Studies Unit, Nuffield Department of Population Health, University of Oxford, Oxford, UK. Electronic address: colin.baigent@ctsu.ox.ac.uk.