University of Oxford - Nuffield Department of Primary Care Health Sciences, University of Oxford - Nuffield Department of Primary Care Health Sciences, University of Oxford - Nuffield Department of Primary Care Health Sciences, affiliation not provided to SSRN, affiliation not provided to SSRN, University of Oxford - Nuffield Department of Primary Care Health Sciences, affiliation not provided to SSRN, Royal College of General Practitioners, University of Oxford - Nuffield Department of Primary Care Health Sciences, Swansea University - Population Data Science, Queen’s University Belfast - Public Health Agency, Swansea University - Population Data Science, Swansea University - Population Data Science, Swansea University - Department of Education and Childhood Studies, University of Strathclyde - Department of Mathematics & Statistics, BREATHE – The Health Data Research Hub for Respiratory Health, Royal College of General Practitioners - Royal College of General Practitioners (RCGP) Research and Surveillance Centre (RSC), University of Edinburgh - Usher Institute, University of Oxford - Nuffield Department of Primary Care Health Sciences and University of Oxford