AntiCoagulants and COGnition

The purpose of this study is to compare the change of global cognitive performance after 52 weeks of intervention among participants with nonvalvular atrial fibrillation (NVAF) receiving rivaroxaban versus a vitamin K antagonist (warfarin). The secondary objectives are to compare, among participants with NVFA receiving rivaroxaban versus warfarin : * the changes of global cognitive performance after 26 weeks of intervention * the changes of executive functions after 26 and 52 weeks of intervention * the changes of episodic memory after 26 and 52 weeks of intervention * the changes of independence and autonomy after 26 and 52 weeks of intervention