title: Warfarin use and stroke risk among patients with nonvalvular atrial fibrillation in a large managed care population.
abstract: BACKGROUND
  Stroke prevention is a goal of atrial fibrillation (AF) management, but discontinuation of warfarin anticoagulation therapy is common.
  
  
  OBJECTIVE
  To investigate the association between warfarin discontinuation and hospitalization for stroke among nonvalvular AF (NVAF) patients enrolled in managed care.
  
  
  METHODS
  Patients with NVAF who initiated warfarin therapy from January 2005 through June 2009 were included. Warfarin discontinuation was defined as a supply gap >60 days without evidence of International Normalized Ratio measurements. Follow-up, which was a variable time period from warfarin initiation until the earlier of death, disenrollment from the health plan, or June 30, 2010, was divided into periods of warfarin treatment and discontinuation. Stroke events were identified based on claims for inpatient stays with a primary diagnosis of stroke or transient ischemic attack. Cox proportional hazards models were constructed to assess the relationship between warfarin discontinuation and incident stroke while adjusting for baseline demographics, stroke and bleeding risk, and comorbidities, as well as time-dependent antiplatelet use, stroke, and bleeding events in the previous warfarin treatment period.
  
  
  RESULTS
  Among warfarin initiators with NVAF (N = 16,253), 51.4% discontinued warfarin therapy at least once during a mean follow-up of 668 days. Stroke risk was significantly greater during warfarin discontinuation periods compared with therapy periods (hazard ratio = 1.60; 95% CI, 1.35-1.90; P < 0.001).
  
  
  CONCLUSIONS
  More than half of patients on warfarin had treatment gaps or discontinued therapy. Therapy gaps were associated with increased stroke risk.
authors.affiliation: Ochsner Clinic Foundation, New Orleans, LA, USA.
authors.forename: Steven B
authors.initials: SB
authors.lastname: Deitelzweig
authors.forename: Erin
authors.initials: E
authors.lastname: Buysman
authors.forename: Brett
authors.initials: B
authors.lastname: Pinsky
authors.forename: Michael
authors.initials: M
authors.lastname: Lacey
authors.forename: Yonghua
authors.initials: Y
authors.lastname: Jing
authors.forename: Daniel
authors.initials: D
authors.lastname: Wiederkehr
authors.forename: John
authors.initials: J
authors.lastname: Graham
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects; D001281:Atrial Fibrillation / Q000150:complications / Q000188:drug therapy*; D005260:Female; D006760:Hospitalization / Q000191:economics; D006801:Humans; D002546:Ischemic Attack, Transient / Q000209:etiology*; D008297:Male; D008329:Managed Care Programs / Q000191:economics; D055118:Medication Adherence; D008875:Middle Aged; D012307:Risk Factors; D020521:Stroke / Q000191:economics / Q000209:etiology*; D013997:Time Factors; D014859:Warfarin / Q000008:administration & dosage* / Q000009:adverse effects*; D055815:Young Adult
chemical_list: D000925:Anticoagulants; D014859:Warfarin
keywords: anticoagulant; claims analysis; managed care; risk assessment; stroke