Abstention from cigarette smoking is recommended for patients who have never smoked on the basis of epidemiological studies showing a consistent and overwhelming relationship between smoking and both ischemic stroke and SAH (Class I; Level of Evidence B). Meschia et al Guidelines for the Primary Prevention of Stroke 3773 3. Community-wide or statewide bans on smoking in public spaces are reasonable for reducing the risk of stroke and MI (Class IIa; Level of Evidence B). Atrial Fibrillation AF, even in the absence of cardiac valvular disease, is associ- ated with a 4- to 5-fold increased risk of ischemic stroke result- ing from embolism of stasis-induced thrombi forming in the left atrial appendage (LAA).370 About 2.3 million Americans have either sustained or paroxysmal AF.370 Embolism of appendage thrombi associated with AF accounts for 10% of all ischemic strokes and an even higher fraction in the very elderly in the United States.371 The absolute stroke rate aver- ages 3.5%/y for 70-year-old individuals with AF, but the risk varies 20-fold among patients, depending on age and other clinical features (see below).372,373 AF is also an independent predictor of increased mortality.374 Paroxysmal AF increases stroke risk similar to sustained AF.375 There is an important opportunity for primary stroke pre- vention in patients with AF because the dysrhythmia is diag- nosed before stroke in many patients. However, a substantial minority of AF-related stroke occurs in patients without a prior diagnosis of the condition. 