BACKGROUND It is unclear whether the overall effectiveness and safety of direct oral anticoagulants (DOACs) are consistent in patients with nonvalvular atrial fibrillation (AF) and extremely low body weight (<50 kg).

OBJECTIVES This study compared DOACs with warfarin in AF patients with low body weight.

METHODS Using data from the Korean National Health Insurance Service database from January 2014 to December 2016, AF patients with body weight ≤60 kg and who were treated with oral anticoagulants (n = 14,013 taking DOACs and n = 7,576 taking warfarin) were included and examined for ischemic stroke, intracranial hemorrhage (ICH), gastrointestinal bleeding, major bleeding, all-cause death, and composite outcome. The propensity score weighting was used to balance the 2 groups.

RESULTS Baseline characteristics were well balanced between the 2 groups (mean age 73 years, mean CHA₂DS₂-VASc score 4, and 28% of patients weighed <50 kg). DOACs were associated with lower risks of ischemic stroke (hazard ratio [HR]: 0.591; 95% confidence interval [CI]: 0.510 to 0.686) and major bleeding (HR: 0.705; 95%: CI 0.601 to 0.825), which were caused by a reduction in ICH (HR: 0.554; 95% CI: 0.429 to 0.713) compared with warfarin. DOAC improved the net clinical benefit compared with warfarin (HR for composite outcome: 0.660; 95% CI: 0.606 to 0.717), and this was consistent in patients who weighed <50 kg (HR for composite outcome: 0.665; 95% CI: 0.581 to 0.762).

CONCLUSIONS In this real-world Asian AF population with low body weight, DOACs showed better effectiveness and safety than warfarin. These results were consistent in patients with extremely low body weight. Regular dosages of DOACs showed comparable results as reduced dosages of DOACs in both effectiveness and safety.