title: Socioeconomic status and risk of hemorrhage during warfarin therapy for atrial fibrillation: A population-based study.
abstract: BACKGROUND
  Among patients taking warfarin, lower socioeconomic status is associated with poorer control of anticoagulation. However, the extent to which socioeconomic status influences the risk of hemorrhage is unknown. We examined the extent to which socioeconomic status influences the risk of hemorrhage in older individuals newly commencing warfarin therapy for atrial fibrillation.
  
  
  METHODS
  We conducted a population-based cohort study of individuals 66 years or older with atrial fibrillation who commenced warfarin therapy between April 1, 1997, and November 30th 2011, in Ontario, Canada. We used neighborhood-level income quintiles as a measure of socioeconomic status. The primary outcome was an emergency department visit or hospitalization for hemorrhage, and the secondary outcome was fatal hemorrhage.
  
  
  RESULTS
  We studied 166,742 older patients with atrial fibrillation who commenced warfarin therapy. Of these, 16,371 (9.8%) were hospitalized for hemorrhage during a median follow-up of 369 (interquartile range 102-865) days. After multivariable adjustment using Cox proportional hazards regression, we found that those in the lowest-income quintile faced an increased risk of hospitalization for hemorrhage relative to those in the highest quintile (adjusted hazard ratio 1.18, 95% CI 1.12-1.23). Similarly, the risk of fatal hemorrhage (n = 1,802) was increased in the lowest-income relative to the highest-income quintile (adjusted hazard ratio 1.28, 95% CI 1.11-1.48).
  
  
  CONCLUSIONS
  Among older individuals receiving warfarin therapy for atrial fibrillation, lower socioeconomic status is a risk factor for hemorrhage and hemorrhage-related mortality. This factor should be carefully considered when initiating and monitoring warfarin therapy.
authors.affiliation: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada; Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Alex M
authors.initials: AM
authors.lastname: Cressman
authors.affiliation: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Erin M
authors.initials: EM
authors.lastname: Macdonald
authors.affiliation: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Yao
authors.affiliation: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada; Institute of Health Policy, Management and Evaluation, Toronto, Ontario, Canada.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Austin
authors.affiliation: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada; Institute of Health Policy, Management and Evaluation, Toronto, Ontario, Canada; The Leslie Dan Faculty of Pharmacy, Toronto, Ontario, Canada; Applied Health Research Centre (AHRC), Li Ka Shing Knowledge Institute of St Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Tara
authors.initials: T
authors.lastname: Gomes
authors.affiliation: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada; Institute of Health Policy, Management and Evaluation, Toronto, Ontario, Canada.
authors.forename: John Michael
authors.initials: JM
authors.lastname: Paterson
authors.affiliation: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada; Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada; Institute of Health Policy, Management and Evaluation, Toronto, Ontario, Canada; Division of General Internal Medicine, University Health Network, Toronto, Ontario, Canada.
authors.forename: Moira K
authors.initials: MK
authors.lastname: Kapral
authors.affiliation: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada; Institute of Health Policy, Management and Evaluation, Toronto, Ontario, Canada; The Leslie Dan Faculty of Pharmacy, Toronto, Ontario, Canada; Applied Health Research Centre (AHRC), Li Ka Shing Knowledge Institute of St Michael's Hospital, Toronto, Ontario, Canada; Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada; Department of Medicine, St Michael's Hospital, Toronto, Ontario, Canada.
authors.forename: Muhammad M
authors.initials: MM
authors.lastname: Mamdani
authors.affiliation: The Institute for Clinical Evaluative Sciences, Toronto, Ontario, Canada; Department of Medicine, Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada; Institute of Health Policy, Management and Evaluation, Toronto, Ontario, Canada; Sunnybrook Research Institute, Toronto, Ontario, Canada. Electronic address: david.juurlink@ices.on.ca.
authors.forename: David N
authors.initials: DN
authors.lastname: Juurlink
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000009:adverse effects*; D001281:Atrial Fibrillation / Q000150:complications / Q000188:drug therapy*; D005260:Female; D006470:Hemorrhage / Q000139:chemically induced* / Q000401:mortality; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D007182:Income / Q000706:statistics & numerical data*; D008297:Male; D015999:Multivariate Analysis; D009864:Ontario; D016016:Proportional Hazards Models; D012111:Residence Characteristics / Q000706:statistics & numerical data; D012306:Risk; D012307:Risk Factors; D012923:Social Class; D020521:Stroke / Q000209:etiology / Q000517:prevention & control*; D014859:Warfarin / Q000009:adverse effects*
chemical_list: D000925:Anticoagulants; D014859:Warfarin