[1] Univ Edinburgh, Ctr Populat Hlth Sci, Sch Med, Edinburgh EH8 9AG, Midlothian, Scotland
[2] Newcastle Univ, Inst Hlth & Soc, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England
[3] Univ Oxford, Dept Primary Hlth Care, Oxford, England
[4] Univ Oxford, Diabet Trials Unit, Oxford Ctr Diabet Endocrinol & Metab, Oxford, England