Footnotes

• Contributors PNR as corresponding and sole author acts as guarantor. He was solely responsible for the manuscript conception and design; analysis and interpretation of data; drafted the article; and final approval 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 None declared.

• Provenance and peer review Commissioned; internally peer reviewed.

• Data sharing statement No applicable.