Published on in Vol 21, No 11 (2019): November
Preprints (earlier versions) of this paper are
available at
https://preprints.jmir.org/preprint/14343, first published
.
1 Primary Care Unit, Department of Public Health and Primary Care, University of Cambridge, Cambridge, United Kingdom
2 Medical Research Council Epidemiology Unit, University of Cambridge, Cambridge, United Kingdom
3 Barking, Havering, and Redbridge University Hospitals Trust, London, United Kingdom