Safety and Effectiveness of Apixaban in Very Elderly Patients with Atrial Fibrillation: A Retrospective Analysis of Japanese Administrative Claims Data

INTRODUCTION: Anticoagulation is a well-established treatment for patients with atrial fibrillation (AF) for the prevention of stroke/systemic embolism (SE). However, although nearly all elderly patients with AF are at risk for thrombotic events, they also have a heightened risk of bleeding, and evidence regarding the optimal anticoagulation regimen in very elderly patients remains limited. This study aimed to evaluate the safety and effectiveness of apixaban versus warfarin in a cohort of very elderly patients with AF in Japan. METHODS: This was a retrospective analysis of administrative claims for patients with AF newly initiated on apixaban or warfarin from acute care hospitals. Clinical and demographic characteristics were balanced between cohorts using an inverse probability of treatment weighting with stabilized weights (s-IPTW) method. Prespecified subgroup analyses were also conducted to assess treatment interaction with some baseline/demographic factors. RESULTS: A total of 77,814 eligible patients with AF were balanced between the apixaban group (N = 33,834) and warfarin group (N = 43,671) using s-IPTW. The incidence of stroke/SE-primary effectiveness outcome-was 55.8 and 75.2 per 1000 person-years and that of major bleeding-primary safety outcome-was 17.3 and 25.3 per 1000 person-years in the apixaban and warfarin groups, respectively. Apixaban was associated with a significantly lower risk of stroke/SE (hazard ratio [HR], 0.75; 95% confidence interval [CI] [0.71-0.80], P < 0.001) and major bleeding (HR, 0.69; 95% CI [0.62-0.76], P < 0.001). Consistent trends were observed across all prespecified secondary outcomes. Additionally, there was no evidence of interaction between treatment and the variables examined, such as age, number of medications, Charlson Comorbidity Index, and activities of daily living. CONCLUSIONS: In very elderly patients with AF, apixaban was associated with a significantly lower risk of stroke/SE and bleeding compared with warfarin. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT05438888.