title: Oral anticoagulation, aspirin, or no therapy in patients with nonvalvular AF with 0 or 1 stroke risk factor based on the CHA2DS2-VASc score.
abstract: BACKGROUND
  Even a single additional stroke risk factor in patients with atrial fibrillation may confer a risk of stroke. However, there is no consensus on how best to treat these patients.
  
  
  OBJECTIVE
  Our objective was to investigate the risk of stroke and bleeding and the impact of antithrombotic therapy among low-risk patients, i.e., with 0 or 1 CHA2DS2-VASc (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, stroke/transient ischemic attack, vascular disease, age 65 to 74 years, sex category) score risk factor.
  
  
  METHODS
  The nationwide cohort for this study was established by linking data from the Danish Civil Registration System, the Danish National Patient Register, and the Danish National Prescription Registry. We studied 39,400 patients discharged with incident nonvalvular atrial fibrillation with 0 or 1 CHA2DS2-VASc risk factor; 23,572 were not treated, 5,353 were initiated on aspirin, and 10,475 were initiated on warfarin.
  
  
  RESULTS
  Stroke event rates for untreated low-risk patients (CHA2DS2-VASc = 0 [male], 1 [female]) were 0.49 per 100 person-years at 1 year and 0.47 per 100 person-years at full follow-up (intention-to-treat). Bleeding event rates among untreated low-risk patients were 1.08 per 100 person-years at 1 year and 0.97 at full follow-up. The presence of 1 additional stroke risk factor (CHA2DS2-VASc = 1 [male], = 2 [female]) among untreated patients increased the stroke rate at 1 year to 1.55 per 100 person-years, representing a significant 3.01-fold increase. At the 1-year follow-up, bleeding increased 2.35-fold, and death increased 3.12-fold.
  
  
  CONCLUSIONS
  Low-risk patients (CHA2DS2-VASc = 0 [male], 1 [female]) have a truly low risk for stroke and bleeding. With 1 additional stroke risk factor (CHA2DS2-VASc = 1 [male], = 2 [female]), there was a significant increase in event rates (particularly mortality) if nonanticoagulated.
authors.affiliation: Aalborg Thrombosis Research Unit, Department of Clinical Medicine, Faculty of Health, Aalborg University, Aalborg, Denmark; University of Birmingham Centre for Cardiovascular Sciences, City Hospital, Birmingham, United Kingdom. Electronic address: g.y.h.lip@bham.ac.uk.
authors.forename: Gregory Y H
authors.initials: GY
authors.lastname: Lip
authors.affiliation: Aalborg Thrombosis Research Unit, Department of Clinical Medicine, Faculty of Health, Aalborg University, Aalborg, Denmark; Department of Cardiology, AF Study Group, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: Flemming
authors.initials: F
authors.lastname: Skjøth
authors.affiliation: Aalborg Thrombosis Research Unit, Department of Clinical Medicine, Faculty of Health, Aalborg University, Aalborg, Denmark.
authors.forename: Lars Hvilsted
authors.initials: LH
authors.lastname: Rasmussen
authors.affiliation: Aalborg Thrombosis Research Unit, Department of Clinical Medicine, Faculty of Health, Aalborg University, Aalborg, Denmark; Department of Cardiology, AF Study Group, Aalborg University Hospital, Aalborg, Denmark.
authors.forename: Torben Bjerregaard
authors.initials: TB
authors.lastname: Larsen
mesh_terms: D000284:Administration, Oral; D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage*; D001241:Aspirin / Q000008:administration & dosage*; D001281:Atrial Fibrillation / Q000175:diagnosis / Q000188:drug therapy* / Q000453:epidemiology; D001777:Blood Coagulation / Q000187:drug effects; D015331:Cohort Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D012042:Registries; D012307:Risk Factors; D020521:Stroke / Q000175:diagnosis / Q000453:epidemiology / Q000517:prevention & control*
chemical_list: D000925:Anticoagulants; D001241:Aspirin
keywords: atrial fibrillation; bleeding; stroke; thromboembolism; warfarin