The link between pneumonia and proton pump inhibitors can be explained by confounding factors, according to new research published in The BMJ.

The retrospective study involving three separate analyses and 160,000 new PPI users found that while a crude association existed between PPI prescriptions and an increased rate of community acquired pneumonia, the link could be explained by an underlying increased risk of pneumonia in patients preceding a PPI prescription.

“Patients’ characteristics, comorbidity, and severity of gastro-oesophageal reflex disease were probably the main contributors to the increased risk of pneumonia observed in patients who received PPIs,” the study authors said.

An accompanying editorial noted that many previous studies had reported increases in risk of pneumonia after a relatively short period of exposure.

“It is not biologically plausible for PPIs to increase the risk of community acquired pneumonia within such a short timeframe, suggesting the presence of protopathic bias or reverse causality (that is, PPIs were prescribed to treat the early symptoms of pneumonia such as chest pain, mistakenly attributed to reflux),” it concluded.