[1] Univ Glasgow, Inst Hlth & Well Being, MRC CSO Social & Publ Hlth Sci Unit, Glasgow, Lanark, Scotland
[2] Univ Glasgow, Inst Hlth & Well Being, Robertson Ctr Biostat, Glasgow, Lanark, Scotland
[3] Univ Exeter, Coll Med & Hlth, Exeter, Devon, England
[4] Univ Exeter, Med Sch Primary Care, Smeall Bldg,St Lukes Campus, Exeter, Devon, England