A previous study reported a significant protective effect of ACE inhibitors on outpatient pneumonia among people with diabetes and a general population.15,16 In addition, a dose–effect relationship was reported between ACE inhibitor use and outpatient pneumonia in diabetes patients.15 We selected pneumonia requiring hospitalization, but not outpatient pneumonia, as an outcome variable, because discharge diagnoses codes are more accurate than outpatient coding. Here, ACE is linked to diabetes mellitus.