Footnotes

• Contributors SK: manuscript writing. MZK: manuscript writing and data analysis. MSK: manuscript writing. SG: critical review of manuscript. MUK: critical review of manuscript. RAK: critical review of manuscript. HJW: critical review of manuscript and study design. EDM: study design and critical review of manuscript. SK and MZK are primary coauthors.

• 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.