[1] Queen Mary Univ London, Wolfson Inst Populat Hlth Sci, Ctr Primary Care, Barts & London Sch Med & Dent, London, England
[2] Univ Manchester, Hlth Serv Res & Primary Care, Div Populat Hlth, Manchester, England
[3] UCL, Dept Primary Care & Populat Hlth, Ehlth Unit, London, England
[4] Queen Mary Univ London, Wolfson Inst Populat Hlth Sci, Barts & London Sch Med & Dent, Ctr Primary Care, Yvonne Carter Bldg 58 Turner St, London E1 2AB, England