Footnotes

• Twitter @oshea_jem

• Contributors JA contributed to the design of the systematic review, independently reviewed the journal titles, abstracts and full-text articles; drafted and revised the manuscript; and approved the final manuscript as submitted. JO contributed to the design of the systematic review, reviewed and revised the manuscript and approved the final manuscript as submitted.

• 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.

• Patient consent for publication Not required.

• Provenance and peer review Not commissioned; externally peer reviewed.