Background: This sub-analysis of the ANAFIE Registry, a prospective, observational study of >30,000 Japanese non-valvular atrial fibrillation (NVAF) patients aged ≥75 years, assessed the prevalence of direct oral anticoagulant (DOAC) under-dose prevalence, identified the factors of under-dose prescriptions, and examined the relationship between DOAC dose and clinical outcomes.Methods and Results: Patients, divided into 5 groups by DOAC dose (standard, over-, reduced, under-, and off-label), were analyzed for background factors, cumulative incidences, and clinical outcome risk. Endpoints were stroke/systemic embolic events (SEE), major bleeding, and all-cause death during the 2-year follow-up. Of 18,497 patients taking DOACs, 20.7%, 3.8%, 51.6%, 19.6%, and 4.3%, were prescribed standard, over-, reduced, under-, and off-label doses. Factors associated with under-dose use were female sex, age ≥85 years, reduced creatinine clearance, history of major bleeding, polypharmacy, antiplatelet agents, heart failure, dementia, and no history of catheter ablation or cerebrovascular disease. After confounder adjustment, under-dose vs. standard dose was not associated with the incidence of stroke/SEE or major bleeding but was associated with a higher mortality rate. Patients receiving an off-label dose showed similar tendencies to those receiving an under-dose; that is, they showed the highest mortality rates for stroke/SEE, major bleeding, and all-cause death.
Conclusions: Inappropriate low DOAC doses (under- or off-label dose) were not associated with stroke/SEE or major bleeding but were associated with all-cause death.
Keywords: Direct oral anticoagulants; Elderly; Non-valvular atrial fibrillation; Off-label dosing; Under-dose.