Footnotes

• Contributors LM-O: drafting/revision of the manuscript for content, including medical writing for content; major rolein the acquisition of data. JC: drafting/revision of the manuscript for content, including medical writing for content; major role inthe acquisition of data. SM: drafting/revision of the manuscript for content, including medical writing for content. TC: drafting/revision of the manuscript for content, including medical writing for content; major role inthe acquisition of data; study concept or design; analysis or interpretation of data; supervision.

• Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

• Competing interests None declared.

• Provenance and peer review Not commissioned; externally peer reviewed by Simon Rinaldi, Oxford, UK.