Acid-suppressive drugs and community-acquired pneumonia.

Background: Acid suppression may increase the risk of community-acquired pneumonia. We investigated this association in the United Kingdom primary care system taking account of the potential for confounding by indication.

Methods: We identified patients aged 20-79 years in The Health Improvement Network database with a new diagnosis of pneumonia between 2000 and 2005 (n = 7297). Cases were validated by manual review and compared with age- and sex-matched controls (n = 9993). Using unconditional logistic regression, we estimated the relative risk (RR) of pneumonia associated with current use of acid-suppressive drugs compared to nonuse.

Results: Newly diagnosed community-acquired pneumonia was increased with current use of proton pump inhibitors (RR = 1.16 [95% confidence interval 1.03-1.31]) but not H2-receptor antagonists (0.98 [0.80-1.20]). An increased risk of pneumonia was evident only in the first 12 months of treatment with proton pump inhibitors. There was some evidence of a dose response. Among patients taking proton pump inhibitors for less than 1 year, the risk of community-acquired pneumonia was stronger when current use was for dyspepsia or peptic ulcer (1.73 [1.29-2.34]) than for gastroesophageal reflux disease or prevention of upper gastrointestinal injury associated with aspirin or nonsteroidal anti-inflammatory drugs (1.22 [0.97-1.52]).

Conclusions: We observed a small increase in the risk of community-acquired pneumonia associated with current proton pump inhibitor use, particularly during the first 12 months of treatment and at higher doses. This may be due in part to the underlying indication.