Background & AimsIn patients with atrial fibrillation (AF) receiving direct oral anticoagulant (DOAC), upper gastrointestinal bleeding (UGIB) is a serious complication. There are limited data on the benefit of preventive proton pump inhibitor (PPI) use to reduce the risk of UGIB in DOAC users. MethodsWe included patients with AF receiving DOAC from 2015 to 2020 based on the Korean Health Insurance Review and Assessment database. The propensity score (PS) weighting method was used to compare patients with PPI use and those without PPI use. The primary outcome was hospitalization for UGIB. Weighted hazard ratios (HR) and corresponding 95% confidence intervals (CI) were evaluated using the Cox proportional hazards regression model. ResultsA total of 165,624 patients were included (mean age: 72±11 years; mean CHA2DS2-VASc score: 4.3±1.8; mean HAS-BLED score: 3.3±1.2). Among them, 99,868 and 65,756 were in the non-PPI group and PPI group, respectively. During a median follow-up of 1.5 years, the PPI group was associated with lower risks of hospitalization for UGIB and UGIB requiring RBC transfusion than non-PPI group [weighted HR (95% CI): 0.825 (0.761-0.894) and 0.798 (0.717-0.887), respectively, both p<0.001]. The benefits of PPI on the risk of hospitalization for UGIB were greater in those with older age (≥75 years), higher HAS-BLED score (≥3), prior UGIB history, and concomitant use of antiplatelet agent (all p-for-interaction<0.1). Low-dose PPI was consistently associated with a lower risk of significant UGIB [adjusted HR: 0.564 (0.504-0.631), p<0.001]. ConclusionsIn this large Asian cohort of patients with AF on DOAC, PPI co-therapy is beneficial for reducing the risk of hospitalization for UGIB, particularly in high-risk patients.