title: Atrial fibrillation, stroke risk, and warfarin therapy revisited: a population-based study.
abstract: OBJECTIVE
  Atrial fibrillation (AF) is a major risk factor for ischemic stroke. This study aims to update the knowledge about AF and associated stroke risk and benefits of anticoagulation.
  
  
  METHODS
  We extracted data from the hospital, specialized outpatient, and primary healthcare and drug registries in a Swedish region with 1.56 million residents. We identified all individuals who had received an AF diagnosis during the previous 5 years; all stroke events during 2010; and patients with AF aged ≥50 years who had received warfarin during 2009.
  
  
  RESULTS
  AF had been diagnosed in 38 446 subjects who were alive at the beginning of 2010 (prevalence of 3.2% in the adult [≥20 years] population); ≈46% received warfarin therapy. In 2010, there were 4565 ischemic stroke events and 861 intracranial hemorrhages. AF had been diagnosed in 38% of ischemic events (≥50% among those aged ≥80 years) and in 23% of intracranial hemorrhages. An AF diagnosis was often lacking in hospital discharge records after stroke events. Warfarin therapy was associated with an odds ratio of 0.50 (confidence interval, 0.43-0.57) for ischemic stroke and, despite an increased risk of intracranial hemorrhage, an odds ratio of 0.57 (confidence interval, 0.50-0.64) for the overall risk for stroke.
  
  
  CONCLUSIONS
  AF is more common than present guidelines suggest. The attributable risk of AF for ischemic stroke increases with age and is close to that of hypertension in individuals aged ≥80 years. Because a majority of patients with AF with increased risk for stroke had not received anticoagulation therapy, there is a large potential for improvement.
authors: From the Department of Health Care Evaluation, Regionens Hus, Gothenburg, Sweden (S.B., B.P.); Department of Cardiology, Danderyd Hospital, Karolinska Institute, Stockholm, Sweden (L.F.); and Department of Molecular and Clinical Medicine/Cardiology, Sahlgrenska Academy, University of Gothenburg, Sweden (L.B.).
authors: Staffan
authors: S
authors: Björck
authors: Bo
authors: B
authors: Palaszewski
authors: Leif
authors: L
authors: Friberg
authors: Lennart
authors: L
authors: Bergfeldt
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000009:adverse effects / Q000627:therapeutic use; D001281:Atrial Fibrillation / Q000150:complications* / Q000453:epidemiology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D006973:Hypertension / Q000150:complications / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D015995:Prevalence; D012042:Registries; D012044:Regression Analysis; D012307:Risk Factors; D020521:Stroke / Q000150:complications* / Q000453:epidemiology; D013548:Sweden / Q000453:epidemiology; D014859:Warfarin / Q000009:adverse effects* / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D014859:Warfarin
keywords: atrial fibrillation; diabetes mellitus; hypertension; intracranial hemorrhage; risk assessment; stroke; thromboembolism