[1] Oxford Brookes Univ, Sch Hlth & Social Care, Oxford OX3 0FL, England
[2] Univ Oxford, Dept Primary Care, Oxford, England
[3] Univ Edinburgh, Edinburgh, Midlothian, Scotland
[4] Cardiff Univ, N Wales Clin Sch, Dept Primary Care & Publ Hlth, Sch Med, Cardiff, S Glam, Wales