Community acquired pneumonia incidence before and after proton pump inhibitor prescription: population based study.

Abstract

<b>Objective</b> To examine the risk of community acquired pneumonia before and after prescription of proton pump inhibitor (PPI) and assess whether unmeasured confounding explains this association.<b>Design</b> Cohort study and self controlled case series.<b>Setting</b> Clinical Practice Research Datalink (1990 to 2013) in UK.<b>Participants</b> Adult patients with a new prescription for a PPI individually matched with controls.<b>Main outcome measures</b> Association of community acquired pneumonia with PPI prescription estimated by three methods: a multivariable Cox model comparing risk in PPI exposed patients with controls, corrected for potential confounders; a self controlled case series; and a prior event rate ratio (PERR) analysis over the 12 month periods before and after the first PPI prescription.<b>Results</b> 160 000 new PPI users were examined. The adjusted Cox regression showed a risk of community acquired pneumonia 1.67 (95% confidence interval 1.55 to 1.79) times higher for patients exposed to PPI than for controls. In the self controlled case series, among 48 451 PPI exposed patients with a record of community acquired pneumonia, the incidence rate ratio was 1.19 (95% confidence interval 1.14 to 1.25) in the 30 days after PPI prescription but was higher in the 30 days before a PPI prescription (1.92, 1.84 to 2.00). The Cox regressions for prior event rate ratio similarly showed a greater increase in community acquired pneumonia in the year before than the year after PPI prescription, such that the analysis showed a reduced relative risk of pneumonia associated with PPI use (prior event rate ratio 0.91, 95% confidence interval 0.83 to 0.99).<b>Conclusion</b> The association between the use of PPIs and risk of community acquired pneumonia is likely to be due entirely to confounding factors.