Funding for this research was provided by:
Medical Research Council
Received: 26 April 2018
Accepted: 12 July 2018
First Online: 16 August 2018
Ethics approval and consent to participate
: The study was conducted in line with ethics applications approved by the Health Research Authority and NHS Research Ethics Service Committee, London, Queen Square. All individuals gave written informed consent to participate.
: Not applicable.
: The authors declare that they have no competing interests.
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