Data sources
We used data from the IQVIA Medical Research Database (IMRD) (previously called The Health Improvement Network (THIN)), an electronic health records database of general practitioner (GP) based healthcare covering 839 practices and 19 million individuals in the UK. The IMRD was established in 2003 as a collaboration between the company owning Vision (In Practice Systems) and the CSD Medical Research Group (now Quintiles IMS). The database contains computerised information on socio-demographics, anthropometric characteristics, lifestyle factors, and details from visits to GPs (i.e., prescriptions, diagnosis, diagnoses and interventions from specialist referrals, hospital admissions, and results of laboratory tests). The READ classification system is used to code specific diagnoses [