Funding for this research was provided by:
Medical Research Council (RA2497)
Received: 22 October 2019
Accepted: 3 July 2020
First Online: 18 July 2020
Ethics approval and consent to participate
: Ethical approval for this project was granted by the Usher Institute Research Ethics Committee at the University of Edinburgh (ethical approval code 1764). All participants provided written informed consent.
: Not applicable.
: All authors are active researchers in public health. The authors have no other competing interests to declare.