Tran T, et al. - Considering discrepancies among some observational studies regarding the effectiveness of anti-acid therapy on mortality in idiopathic pulmonary fibrosis (IPF), researchers reviewed all studies evaluating if immortal time bias explains these discrepancies. Observational studies affected by immortal time bias showed anti-acid therapy having apparently beneficial effects on mortality in patients with IPF. The effectiveness of anti-acid therapy in IPF thus remained uncertain and required to be reassessed with more accurate observational study methods and randomized trials.