Footnotes

• Twitter @gonsolisg

• Contributors BJ and TY developed the initial idea of research. GS-G performed the literature search. BJ and GS-G collected and analysed the data, and drafted the manuscript. TY and BJ reviewed the manuscript.

• 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.