Footnotes

• Handling editor Richard Body

• Contributors D-AL and W-CL conceived the study and designed the trial. W-CL, W-TC and C-HH supervised the conduct of the trial and data collection. J-YC, Y-CC, Y-CK and C-HH undertook data collection and managed the data, including quality control. D-AL and W-CL analysed the data. D-AL drafted the manuscript and W-CL revised it. All authors contributed substantially to its revision. W-CL takes responsibility for the paper.

• 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.

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