Proton pump inhibitor use and risk of pneumonia: a self-controlled case series study

Abstract

Abstract Background Recent research indicates that use of proton pump inhibitors (PPIs) is associated with pneumonia, but existing evidence is inconclusive because of methodological issues. This study aimed to answer whether PPI-use increases risk of pneumonia while taking the methodological concerns of previous research into account. Methods This population-based and nationwide Swedish study conducted in 2005–2019 used a self-controlled case series design. Data came from national registries for medications, diagnoses, and mortality. Conditional fixed-effect Poisson regression provided incidence rate ratios (IRR) with 95% confidence intervals (CI) for pneumonia comparing PPI-exposed periods with unexposed periods in the same individuals, thus controlling for confounding. Analyses were stratified by PPI-treatment duration, sex, age, and smoking-related diseases. Use of histamine type-2 receptor antagonists (used for the same indications as PPIs) and risk of pneumonia was analysed for assessing the validity and specificity of the results for PPI-therapy and pneumonia. Results Among 519,152 patients with at least one pneumonia episode during the study period, 307,709 periods of PPI-treatment occurred. PPI-use was followed by an overall 73% increased risk of pneumonia (IRR 1.73, 95% CI 1.71–1.75). The IRRs were increased across strata of PPI-treatment duration, sex, age, and smoking-related disease status. No such strong association was found between histamine type-2 receptor antagonist use and risk of pneumonia (IRR 1.08, 95% CI 1.02–1.14). Conclusions PPI-use seems to be associated with an increased risk of pneumonia. This finding highlights a need for caution in using PPIs in individuals with a history of pneumonia.