title: Age and risk of stroke in atrial fibrillation: evidence for guidelines?
abstract: OBJECTIVE
  Guidelines for the clinical management of patients with atrial fibrillation suggest that treatment strategies for prescribing oral anticoagulant therapy should implicate change at age 60, 65 and 75 years. We examined if there is any threshold concerning risk of stroke by age.
  
  
  METHODS
  We identified 141,493 subjects, aged 40-89 years, with an incident hospital diagnosis of nonvalvular atrial fibrillation or flutter and no previous or concomitant diagnosis of stroke in the Danish National Registry of Patients from January 1, 1980, to December 31, 2002. The subjects were followed in the Danish National Registry of Patients for the occurrence of an incident diagnosis of stroke of any nature and in the Danish Civil Registration System for emigration and vital status. We examined the risk of stroke by age in men and women using Cox regression models, which included age categorized in intervals, linear splines of age with cut points at age 60 and 75 years, or at age 65 and 75 years. We also analyzed age as a continuous variable in linear and polynomial regression models.
  
  
  RESULTS
  During follow-up 15,964 incident strokes were reported to the Danish National Registry of Patients. The risk of stroke increased by increasing age at baseline. We did not find any evidence for a threshold concerning risk of stroke by age, and the best model fit was obtained in a third-order polynomial regression model.
  
  
  CONCLUSIONS
  The risk of stroke increased gradually by increasing age, and we could not detect any threshold concerning risk of stroke by age.
authors.affiliation: Department of Cardiology A, Aarhus University Hospital, Aarhus, Denmark. malfr@sc.aaa.dk
authors.forename: Lars
authors.initials: L
authors.lastname: Frost
authors.forename: Ljubica
authors.initials: L
authors.lastname: Vukelic Andersen
authors.forename: John
authors.initials: J
authors.lastname: Godtfredsen
authors.forename: Leif Spange
authors.initials: LS
authors.lastname: Mortensen
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001281:Atrial Fibrillation / Q000150:complications* / Q000453:epidemiology*; D001282:Atrial Flutter / Q000150:complications / Q000453:epidemiology; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005500:Follow-Up Studies; D017408:Guidelines as Topic; D006801:Humans; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012042:Registries; D012307:Risk Factors; D020521:Stroke / Q000453:epidemiology* / Q000209:etiology*; D016896:Treatment Outcome