Fourteen studies (n=84,835) were included in the review. These were two RCTS (n=7,191), seven prospective studies (n=4,035, including six cohort and one case-control study), and five retrospective studies (n=73,609 including two cohort and three case-control studies).
Random Controlled Trials (RCTs): One RCT (n=70) reported a statistically significant reduction in mortality in the ACE inhibitor group compared with the usual-care group. The larger RCT (n=7,121) reported no significant difference in pneumonia between ACE inhibitors and placebo for the entire study group, but subgroup analysis showed a significant reduction in pneumonia in patients of Asian origin who received ACE inhibitors.
Prospective studies: Six studies reported a significant reduction in community-acquired pneumonia development in ACE inhibitor groups compared to a variety of control groups. One study reported no significant difference in mortality between ACE inhibitors and calcium-channel blockers.
Retrospective studies: Three of four studies reported no significant difference in pneumonia between patients receiving ACE inhibitors and the control group. One study reported a reduction in mortality in ACE inhibitor group.
The authors stated that eight of 10 studies that included patients of Asian origin reported a significant benefit in ACE inhibitor groups. One of five studies that included patients of non-Asian origin reported beneficial effects associated with ACE inhibitors.
The authors stated that overall all but one of the studies which found a positive effect were conducted primarily among Asian populations. It was not possible to verify this since no details of ethnicity were reported for individual studies.