Key result
Oral anticoagulant initiation is not associated with reduced ischemic stroke risk in incident AF.
Why the study?
The impact of a first prescription of oral anticoagulation on ischemic stroke and major bleeding among Medicare beneficiaries with AF was not known.
Does the first prescription of an oral anticoagulant reduce the composite of cerebral or retinal ischemic stroke in older Medicare beneficiaries with incident atrial fibrillation?
Cohort (n=144,969)
Does the first prescription of an oral anticoagulant reduce the composite of cerebral or retinal ischemic stroke in older Medicare beneficiaries with incident atrial fibrillation?
In older, real-world Medicare beneficiaries with incident atrial fibrillation, initiation of oral anticoagulation did not reduce ischemic stroke but increased major bleeding, reflecting appropriate baseline selection of healthier, higher-benefit patients for therapy by clinicians.
Answers are grounded in this paper and cite their sources.
No ischemic stroke reduction seen with initial anticoagulation in older Medicare AF patients; leaves open questions on selection bias and real-world effectiveness.
BACKGROUND: The impact of first prescription of oral anticoagulation on ischemic stroke and major bleeding events among Medicare beneficiaries with atrial fibrillation (AF) is not known. METHODS: A retrospective, observational, cohort study was performed based on a 5% sample of United States fee-for-service Medicare beneficiaries aged ≥66 years who developed AF from 2007 to 2020. The principal exposure was first prescription of an oral anticoagulant. The primary effectiveness end point was ischemic stroke (including cerebral or retinal ischemic stroke [central retinal artery occlusion]). The primary safety end point was major bleeding. To reduce the impact of selection bias and immortal time bias, unadjusted and adjusted hazard ratios (HRs) and rate differences were computed in a dataset comprised of pooled, sequential clinical trial replicates starting 1 month apart. RESULTS: In total, 144,969 patients (60.8% female; mean age 77.7 years [standard deviation (SD) 7.1]) were included in the study. First prescription of oral anticoagulation was not associated with a reduced hazard of ischemic stroke (adjusted HR [aHR] 1.01 [95% confidence interval (CI): 0.97-1.05]). However, first prescription of oral anticoagulation was associated with an increased hazard of a major bleeding event (aHR 1.38 [95% CI: 1.36-1.40]) and increased hazards of intracerebral hemorrhage (ICH) and major gastrointestinal hemorrhage. CONCLUSIONS: In this cohort study of Medicare beneficiaries aged 66 years and older with incident AF, the first anticoagulant prescription was not associated with a reduced hazard of ischemic stroke. Furthermore, unadjusted models suggested that clinicians are likely appropriately selecting patients for anticoagulation in routine clinical practice.
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Lusk et al. (2025) conducted a cohort in Atrial Fibrillation (n=144,969). First prescription of an oral anticoagulant vs. No initiation of oral anticoagulation was evaluated on Composite of cerebral ischemic stroke or retinal ischemic stroke (HR 1.01, 95% CI 0.97-1.05). Among Medicare beneficiaries aged 66 years and older with incident atrial fibrillation, the first prescription of an oral anticoagulant was not associated with a reduced hazard of ischemic stroke (aHR 1.01).
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