Funding for this research was provided by:
Medical Research Council ([MC_ST_U14024])
Received: 17 September 2019
Accepted: 14 January 2020
First Online: 7 February 2020
Ethics approval and consent to participate
: Ethical approval for this study was obtained from University of Glasgow College of Social Sciences Research Ethics Committee in January 2016 (ref: 400150077). Written consent was obtained from each participant. All data were treated confidentially by de-identifying the data.
: Not applicable.
: The authors declare that they have no competing interests.