Footnotes

• Contributors SK conceptualised and designed the study, prepared the protocol, screened studies, abstracted data, completed risk of bias evaluation, performed the analysis and prepared the first draft of the manuscript. KFN and RJJ reviewed the screened studies and analysis, examined, edited and revised the manuscript. All authors approved the final manuscript as submitted and agreed to be accountable for all aspects of the work.

• 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.