Methods:

The investigators conducted a case-population study and consecutively selected patients aged ≥18 years with a PCR-confirmed diagnosis of COVID-19 requiring admission to the hospital from seven hospitals in Madrid, who had been admitted between March 1 and March 24, 2020. As a reference group, they randomly sampled 10 patients per case, individually matched for age, sex, region (i.e., Madrid), and date of admission to hospital (month and day; index date), from Base de datos para la Investigación Farmacoepidemiológica en Atención Primaria (BIFAP), a Spanish primary health care database, in its last available year (2018). The authors extracted information on comorbidities and prescriptions up to the month before index date (i.e., current use) from electronic clinical records of both cases and controls. The outcome of interest was admission to hospital of patients with COVID-19. To minimize confounding by indication, the main analysis focused on assessing the association between COVID-19 requiring admission to hospital and use of RAAS inhibitors compared with use of other antihypertensive drugs. The authors calculated odds ratios (ORs) and 95% confidence intervals (CIs), adjusted for age, sex, and cardiovascular comorbidities and risk factors, using conditional logistic regression. The protocol of the study was registered in the EU electronic Register of Post-Authorization Studies, EUPAS34437.