Use of acid-suppressive drugs and risk of pneumonia: a systematic review and meta-analysis

Background

Observational studies and randomized controlled trials have yielded inconsistent findings about the association between the use of acid-suppressive drugs and the risk of pneumonia. We performed a systematic review and meta-analysis to summarize this association.

Methods

We searched three electronic databases (MEDLINE PubMed], Embase and the Cochrane Library) from inception to Aug. 28, 2009. Two evaluators independently extracted data. Because of heterogeneity, we used random-effects meta-analysis to obtain pooled estimates of effect.

Results

We identified 31 studies: five case–control studies, three cohort studies and 23 randomized controlled trials. A meta-analysis of the eight observational studies showed that the overall risk of pneumonia was higher among people using proton pump inhibitors (adjusted odds ratio OR] 1.27, 95% confidence interval CI] 1.11–1.46, I² 90.5%) and histamine₂ receptor antagonists (adjusted OR 1.22, 95% CI 1.09–1.36, I² 0.0%). In the randomized controlled trials, use of histamine₂ receptor antagonists was associated with an elevated risk of hospital-acquired pneumonia (relative risk 1.22, 95% CI 1.01–1.48, I² 30.6%).

Interpretation

Use of a proton pump inhibitor or histamine₂ receptor antagonist may be associated with an increased risk of both community- and hospital-acquired pneumonia. Given these potential adverse effects, clinicians should use caution in prescribing acid-suppressive drugs for patients at risk.Recently, the medical literature has paid considerable attention to unrecognized adverse effects of commonly used medications and their potential public health impact.¹ One group of medications in widespread use is acid-suppressive drugs, which represent the second leading category of medication worldwide, with sales totalling US$26.9 billion in 2005.²Over the past 40 years, the development of potent acid-suppressive drugs, including proton pump inhibitors, has led to considerable improvements in the treatment of acid-related disorders of the upper gastrointestinal tract.³ Experts have generally viewed proton pump inhibitors as safe.⁴ However, potential complications such as gastrointestinal neoplasia, malabsorption of nutrients and increased susceptibility to infection have caused concern.⁵Of special interest is the possibility that acid-suppressive drugs could increase susceptibility to respiratory infections because these drugs increase gastric pH, thus allowing bacterial colonization.^6,7 Several previous studies have shown that treatment with acid-suppressive drugs might be associated with an increased risk of respiratory tract infections⁸ and community-acquired pneumonia in adults^6,7 and children.⁹ However, the association between use of acid-suppressive drugs and risk of pneumonia has been inconsistent.^10–13Given the widespread use of proton pump inhibitors and histamine₂ receptor antagonists, clarifying the potential impact of acid-suppressive therapy on the risk of pneumonia is of great importance to public health.¹⁴ Previous meta-analyses have focused on the role of acid-suppressive drugs in preventing stress ulcer,^11,13,15 but none have examined pneumonia as the primary outcome.The aim of this study was to summarize the association between the use of acid-suppressive drugs and the risk of pneumonia in observational studies and randomized controlled trials.