Figure 1

Case-population study design

COVID-19 cases requiring admission to hospital were selected consecutively from seven hospitals in Madrid, Spain. Data were collected for ten individuals per case who were matched for age, sex, and index date (day and month) of hospital admission of cases (matched controls) from the 2018 Madrid region database of BIFAP, a national primary health-care database. Drug exposure and comorbidities before the index date (2020 for cases and 2018 for controls) were collected from primary health-care records of the NHS in Madrid: for cases through HORUS (an online platform to access primary-care clinical records from any health-care centre of the NHS in Madrid) and for controls through BIFAP. BIFAP=Base de datos para la Investigación Farmacoepidemiológica en Atención Primaria. NHS=National Health System.