Footnotes

• Contributors MvR was the main investigator, conceptualised and designed the study, coordinated, and supervised data collection, drafted the initial manuscript, and reviewed and revised the manuscript. KH drafted the initial manuscript and reviewed and revised the manuscript. MAKG and TR critically reviewed the manuscript for important intellectual content. ALF and KLPG designed the data collection instruments, collected data, and reviewed and revised the manuscript. FHJvL carried out the initial analyses, and critically reviewed the manuscript for important intellectual content and revised 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 None declared.

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