Aged ; Aged, 80 and over ; Anticoagulants ; therapeutic use ; Aspirin ; therapeutic use ; Atrial Fibrillation ; complications ; drug therapy ; Brain Ischemia ; etiology ; prevention & control ; Dabigatran ; therapeutic use ; Dipyridamole ; therapeutic use ; Female ; Guideline Adherence ; statistics & numerical data ; Humans ; Male ; Middle Aged ; Platelet Aggregation Inhibitors ; therapeutic use ; Practice Guidelines as Topic ; Primary Prevention ; statistics & numerical data ; Pyrazoles ; therapeutic use ; Pyridones ; therapeutic use ; Rivaroxaban ; therapeutic use ; Stroke ; etiology ; prevention & control ; Ticlopidine ; analogs & derivatives ; therapeutic use ; Warfarin ; therapeutic use