Retro=Retrospective Study; CS=Cohort Study; CCS=Case Control Study; COVID-19=coronavirus disease 2019; ACEi=Angiotensin-Converting Enzyme Inhibitor; ARB: Angiotensin Receptor Blocker; COPD=Chronic Obstructive Pulmonary Disease; CKD=Chronic Kidney Disease. Here, ACE is linked to chronic obstructive pulmonary disease.