Age and the risk of warfarin-associated hemorrhage: the anticoagulation and risk factors in atrial fibrillation study.

Anticoagulation therapy with warfarin effectively reduces the risk of ischemic stroke associated with atrial fibrillation but also increases the risk for major hemorrhage.1–4 Although previous randomized trials of warfarin for atrial fibrillation reported low rates of hemorrhage, these studies included few patients aged 80 and older and selected their patients more rigorously than in actual clinical practice.1,5 It is uncertain whether the low bleeding rates observed in trial settings apply to patients with atrial fibrillation in usual clinical care. Prior studies have also provided conflicting evidence as to whether older age is an independent risk factor for warfarin-associated hemorrhage.6–8 As increasing numbers of elderly patients take warfarin for atrial fibrillation,9 more-precise data are needed on hemorrhage rates in the oldest patients. Most observational studies of warfarin did not specifically address the risk of hemorrhage in patients with atrial fibrillation. Studies generally included patients taking warfarin for mechanical heart valves or venous thromboembolic diseases, conditions that may have different clinical characteristics and target anticoagulation intensities than atrial fibrillation. Previous studies also lacked sufficient outcome events to examine the association between age and different types of hemorrhage, an important concern because risk factors and consequences of hemorrhage differ between intracranial and extracranial hemorrhages.10 To address these concerns, data from the large AnTicoagulation and Risk Factors In Atrial Fibrillation (ATRIA) cohort were analyzed to assess whether older age is independently associated with risk of intracranial and extracranial hemorrhage in patients with nonvalvular atrial fibrillation.