1. From the Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK (S.L.L.-F., J.P.S., R.J.S., C.H., F.D.R.H., R.J.M.)
2. School for Primary, Community and Social Care, Keele University, Keele, UK (C.M.)
3. Institute of Cardiovascular Science, University College London, London, UK (B.W.)
4. Department of Public Health and Primary Care, University of Cambridge, Cambridge, UK (J.M.).