Footnotes

• Contributors MJAvdS and LSAT were responsible for conceptualisation, (monitoring and interpreting) data collection, wrote the statistical analysis plan, analysed the data and drafted and revised the final paper. FS and EL were responsible for the conceptualisation, supervised in the data interpretation and reviewed and edited the final paper. CdB was responsible for monitoring and interpreting data collection and reviewed the final paper. EJTV reviewed the final paper.

• Funding This study was funded by a research grant from the TAPS Support Foundation.

• Competing interests None declared.

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