Livingston, and Liberton Hospital, Edinburgh, for identifying patients. We especially thank Dr N Uren, Dr R Fergusson, Dr K Swarski, Dr P Cantley, Ms D Borthwick, and Ms M Smith for help with developing the recruitment strategy. We thank Dr M Dlugoleska of Lothian Health for help with study design. Contributors: See bmj.com Funding: Chief Scientist Office of the Scottish Executive. Competing interests: None declared.