Objective:Coronavirus disease 2019 (COVID-19) is caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Renin-angiotensin-aldosterone-system (RAAS) inhibitors may increase the expression of angiotensin-converting enzyme 2, which is the receptor for SARS-CoV-2 Spike protein. The consequences of using angiotensin-converting enzyme inhibitors (ACEi) and angiotensin receptor blockers (ARB) during the COVID-19 pandemic are unknown.Methods:A retrospective cohort study aiming to identify the odds of severe disease (defined as either hospitalization of ≥14 days, admission to the intensive care unit, or death) associated with exposure to ACEi or ARB was conducted. Adult patients (age ≥18 years) with COVID-19 admitted to the İstanbul Faculty of Medicine Corona Center between March 9 and May 11, 2020, were included. Chronic users of ACEi, ARB, or other antihypertensive drugs were matched according to age, sex, sick days before hospitalization, comorbidities, smoking, number of antihypertensive regimens, doxazosin use, furosemide use, and serum creatinine level. Odds ratios (OR) of having severe disease were calculated.Results:In total, 611 patients were admitted with COVID-19, confirmed by either reverse-transcriptase polymerase chain reaction or computed tomography (CT). There were 363 males, and the age ranged from 18 to 98 years, with an average age of 57±15 years. Of these, 165 participants had severe disease (53 deaths, case fatality rate: 8.7%). Among those with hypertension (n=249), ARB exposure was compatible with decreased odds (OR=0.60, 95% CI: 0.27–1.36, p=0.31) of severe disease though not statistically significant, while ACEi exposure significantly reduced the risk of severe disease (OR=0.37, 95% CI: 0.15–0.87, p=0.03). ACEi exposure was associated with milder infiltrations seen on baseline CT, lower C-reactive protein and ferritin, higher monocytes, shorter hospitalization, and less requirement for specific empirical treatments (favipiravir and meropenem).Conclusion:Our data suggest that exposure to ACEi drugs may have favorable effects in the context of COVID-19 pneumonia.