Inappropriate dosing of direct oral anticoagulants among very older inpatients with atrial fibrillation.

Among very older patients with atrial fibrillation (AF), the frequency of inappropriate direct oral anticoagulant (DOAC) dosing, associated factors, and temporal trends in practice are unknown.This retrospective study included consecutive inpatients aged 80 years or older with a discharge diagnosis of atrial fibrillation who were prescribed DOACs at discharge from Beijing Hospital between January 2018 and August 2023. Patients were stratified into underdosed, overdosed, or recommended dosing groups. Logistic regression analysis was performed to identify risk factors associated with inappropriate dosing, and temporal trends were evaluated using the Cochran-Mantel-Haenszel test.Among 676 inpatients aged ≥ 80 years with AF (mean age 84.4 ± 3.5 years; 53.1% female) who were prescribed a DOAC at hospital discharge (22.9% dabigatran, 62.3% rivaroxaban, 14.8% edoxaban), recommended dosing was observed in 338 patients (50.6%), underdosing in 308 (45.6%), and overdosing in 30 (4.4%). The overall rate of inappropriate dosing was 49.4%. Factors independently associated with underdosing included advanced age (OR = 1.98, 95% CI: 1.52-2.60, p < 0.001), lower creatinine clearance (OR = 0.98, 95% CI: 0.97-0.99, p = 0.01), and discharge from non-internal medicine wards (OR = 2.15, 95% CI: 1.33-3.45, p = 0.002). Overdosing was associated with younger age (OR = 0.38, 95% CI: 0.19-0.75, p = 0.005). Although the proportion of recommended dosing increased over the study period, and inappropriate dosing showed a declining trend, these changes did not reach statistical significance.Inappropriate DOAC dosing, especially underdosing, remains common in very older AF inpatients. This issue persists despite years passing, emphasizing the need for patient-focused, collaborative AF management and thorough prognostic studies.