1. London School of Hygiene and Tropical Medicine; Department of Non-communicable Disease Epidemiology; Keppel Street London UK WC1E 7HT
2. King's College London; Department of Twin Research & Genetic Epidemiology; St. Thomas' Hospital Campus 4th Floor, South Wing, Block D London UK SE1 7EH
3. University of Bristol; MRC Health Services Research Collaboration; Canynge Hall Whiteladies Road Bristol UK BS8 2PR
4. University of Bristol; Department of Social Medicine; Canynge Hall 39 Whatley Road Bristol UK BS8 2PS
5. University of Bristol; School of Social and Community Medicine; Oakfield House Oakfield Grove, Clifton Bristol UK BS8 2BN