CHADS2 Score is used for the risk stratification and treatment recommendation in patients with non-valvular atrial fibrillation (NVAF). NVAF patients with CHADS2 Score ≥2 are at high stroke risk and recommended warfarin for stroke prevention. Those with CHADS2 Score 1 are recommended aspirin or warfarin. However, according to the results of the Japanese Atrial Fibrillation Stroke Trial (JAST), aspirin did not reduce stroke risk and tended to increase bleeding risk in low-risk NVAF patients. Therefore, warfarin is recommended even in those with CHADS2 Score 1. The Birmingham Atrial Fibrillation Treatment of the Aged (BAFTA) Study showed that incidence of ischemic stroke was much lower in warfarin (INR 2–3) group than in aspirin group and incidence of hemorrhagic stroke was similar between both groups among elderly NVAF patients. The results of BAFTA indicated that warfarin is recommended even in elderly NVAF patients.
Efficacy of antiplatelet therapy for primary stroke prevention has not established in patients with asymptomatic brain infarction, carotid disease, or vascular risk factors alone. Thus, we conducted the Japanese Primary Prevention Project with Aspirin in the Elderly with One or More Risk Factors of Vascular Events (JPPP), a large randomized trial of aspirin for primary prevention of vascular events including stroke. However, there is a possibility that a risk reduction of vascular events is less than an increase of bleeding risk in primary prevention. Then, we conducted the Management of Aspirin-Induced Gastro-Intestinal Complications (MAGIC), a multi-center cooperative observational study on endoscopical investigation of gastrointestinal complications with aspirin in patients with vascular diseases including stroke.