1. 'Department of Epidemiology and Public Health, University College London Medical School, 1-19 Torrington Place, London WC1E 6BT, UK,
2. Department of Restorative Dentistry, University of Newcastle Dental School, Framlington Place, Newcastle upon Tyne, NE3 4BW, UK
3. 'Department of Epidemiology and Public Health, University College London Medical School, 1-19 Torrington Place, London WC1E 6BT, UK
4. National Centre for Social Research, London, UK
5. MRC Human Nutrition Research, Downhams Lane, Milton Road, Cambridge CB4 1XJ, UK