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©2013 UpToDate ® Print Email Benefit of anticoagulation in chronic atrial fibrillation is related to age and risk factors Pooled data from the randomized controlled trials of warfarin or aspirin in atrial fibrillation show that the reduction in the stroke rate is associated with age and the presence (plus sign) or absence (minus sign) of at least one risk factor (history of hypertension, history of diabetes, previous transient ischemic attack, or heart failure). Among patients less than 65 years of age, warfarin reduced the rate of stroke only in those with risk factors, while the risk of stroke in those without risk factors was low with or without warfarin therapy. Among patients 65 to 75 years of age without risk factors, aspirin and warfarin were equally effective for stroke prevention, while in those with risk factors warfarin significantly reduced the incidence of stroke; aspirin has not been evaluated in this population. Among patients over 75 years of age without risk factors, warfarin is an effective therapy while aspirin has not been evaluated; in those with risk factors, warfarin, but not aspirin, is an effective therapy for stroke prevention. Data from Ezekowitz MD, Levine JA. JAMA 1999; 99:1830.