1. Barts and The London School of Medicine and Dentistry; Clinical and Diagnostic Oral Sciences, Institute of Dentistry; Queen Mary, University of London Turner Street, Whitechapel London UK E1 2AD
2. MRC Biostatistics Unit; Institute of Public Health Robinson Way Cambridge UK CB2 0SR
3. University College London Medical School; Department of Epidemiology and Public Health; 1-19 Torrington Place London UK WC1E 6BT
4. Peninsula Medical School, Universities of Exeter & Plymouth; Institute of Health and Social Care Research; St Luke's Campus Heavitree Road Exeter UK EX1 2LU