1 Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK.
2 Cardiovascular Biomedical Research Unit, Royal Brompton Hospital, London, UK; National Heart and Lung Institute, Imperial College London, London, UK.
3 Faculty of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, London WC1E 7HT, UK. Electronic address: krishnan.bhaskaran@lshtm.ac.uk.