Footnotes

• Contributors JY: data collection, data analysis, data synthesis and authorship of article. WY: data collection, data analysis, study conception and authorship of article. EK and ST: data collection, data analysis and data synthesis. MM: study conception, data analysis and authorship of article. SO: the guarantor and study conception, data analysis, data synthesis and authorship of article. All authors reviewed the results and approved the final version of 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 Dr SO is on the editorial board of RAPM. The other authors declare no conflicts of interest.

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