Footnotes

• Twitter @DrCGale, @AnnaBasu1

• Contributors DB wrote the first draft. CG, SJ and KO provided and analysed national data. KP made substantial contribution to the manuscript. APB made substantial contribution to the manuscript, and drafted and revised the final 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.