Transparency
Declaration of funding
This letter was not funded.
Declaration of financial/other relationships
J.W.S. has disclosed that he has received a research grant from AstraZeneca. T.M., L.W., D.M.W., E.P. and A.G. have disclosed that they have no significant relationships with or financial interests in any commercial companies related to this study or article.
Acknowledgments
We acknowledge the help of Dr David Price (Morriston Hospital) for his assistance with database management.