Some researchers have postulated that, by facilitating bacterial colonization of the stomach and upper intestine, suppression of gastric acid increases the risk for community-acquired pneumonia (CAP). Proton-pump inhibitors (PPIs) are among the most potent suppressors of gastric-acid secretion and are commonly prescribed — often without clear indications. Attempts to prove an association between PPI exposure and CAP have yielded inconsistent results. Now, researchers have conducted a retrospective, nested case-control study to explore this issue further.
Analysis of linked pharmacy and administrative databases from the New England Veterans Healthcare System yielded 71,985 patients who were newly prescribed PPIs between October 1997 and September 2007. Within this group, 1544 patients developed CAP after PPI initiation. These case patients were matched by age and follow-up duration with 15,440 controls who received new PPI prescriptions during the same period but did not develop CAP. PPI use was categorized as current if the prescription end date was after the index CAP date and past if it preceded this date.
Cases were significantly more likely than controls to have one or more medical comorbidities (in addition to gastroesophageal reflux), to have been hospitalized 
90 days before the diagnosis of CAP, and to have been prescribed other medications possibly linked to CAP. The risk for developing CAP was higher in patients with current PPI use than in those with past use (adjusted odds ratio, 1.29; 95% confidence interval, 1.15–1.45). PPI prescription at a dose exceeding the standard daily dose (significantly more common in case patients than in controls) was also associated with CAP (P=0.012).
Comment: Because the study was retrospective and did not involve review of medical records, the results must be interpreted cautiously. However, the findings do suggest a modest effect of PPIs on the risk for CAP.
— Neil M. Ampel, MD
Published in Journal Watch Infectious Diseases January 18, 2012
