Patients with AF could have a known history of AF (with or without available ECG documentation on admission: Patients with persistent/permanent AF would be in AF, while patients with known paroxysmal AF could be either in AF or in sinus rhythm), have a new AF on admission, or have their first AF in hospital. No AF was defined as no history of AF, or no AF on admission or during the hospitalization. The CHADS2 score, the CHA2DS2-VASc score (cardiac failure or dysfunction, hypertension, age ≥ 75 years [doubled], diabetes, stroke [doubled]-vascular disease, age 65-74 years, and sex category [female]) (whereby 2 points are assigned for a history of stroke or age ≥ 75 years and 1 point each for age 65-74 years, a history of hypertension, diabetes, cardiac failure, and vascular disease),14 and the Global Registry of Acute Coronary Events (GRACE) risk score15 (age, Killip class, heart rate, systolic BP, ST-segment deviation and cardiac arrest at admission, elevated biomarkers of myocardial necrosis, and baseline creatinine level) were calculated from data collected at admission. Table 1 shows the CHADS2 score for patients with and without AF. High scores were few, and the scores were, therefore, grouped into 0, 1, 2, and > 2. The CHADS2 score could not be determined in five patients with AF and three without AF. Survival confirmation and date of death as of January 1, 2007, were obtained from the Swedish National Population Registry, and the incidence of stroke (International Classification of Diseases, Ninth Revision codes 431, 432, 433, or 436, or International Classification of Diseases, Tenth Revision codes I61, I62, I63, or I64) was obtained via linking to the National Swedish Diagnosis Registry for hospitalized patients. Eight patients were lost during the follow-up period because of emigration.