The European respiratory journal : official journal of the European Society for Clinical Respiratory Physiology
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International treatment guidelines for idiopathic pulmonary fibrosis (IPF) give a conditional recommendation for anti-acid therapy. As some observational studies reported discrepant findings on the effectiveness of anti-acid therapy on mortality in IPF, we reviewed all studies to evaluate whether immortal time bias explains these discrepancies. We searched the Embase and MEDLINE databases up to July 2017 for observational studies assessing the effectiveness of anti-acid therapy on mortality in IPF. ⋯ The five studies that avoided immortal time bias reported no effect of anti-acid therapy on mortality (pooled hazard ratio 0.99; 95% CI 0.81-1.22). The apparent beneficial effects of anti-acid therapy on mortality in patients with IPF result from observational studies affected by immortal time bias. Thus, the effectiveness of anti-acid therapy in IPF remains uncertain and needs to be reassessed with more accurate observational study methods and randomised trials.