title: National utilization patterns of warfarin use in older patients with atrial fibrillation: a population-based study of Medicare Part D beneficiaries.
abstract: BACKGROUND
  Although warfarin therapy reduces stroke incidence in patients with atrial fibrillation (AF), the rate of warfarin use in this population remains low. In 2008, the Medicare Part D program was expanded to pay for medications for Medicare enrollees.
  
  
  OBJECTIVE
  To examine rates and predictors of warfarin use in Medicare Part D beneficiaries with AF.
  
  
  METHODS
  This population-based retrospective cohort study used claims data from 41,447 Medicare beneficiaries aged 66 and older with at least 2 AF diagnoses in 2007 and at least 1 diagnosis in 2008. All subjects had continuous Medicare Part D prescription coverage in 2008. Statistical analysis using χ(2) was used to examine differences in warfarin use by patient characteristics (age, ethnicity, sex, Medicaid eligibility, comorbidities, contraindications to warfarin, and whether they visited a cardiologist or a primary care physician [PCP]), CHADS(2) score (congestive heart failure, hypertension, age, diabetes, and stroke or transient ischemic attack; higher scores indicate higher risks of stroke), and geographic regions. Using hierarchical generalized linear models restricted to subjects without warfarin contraindications (n = 34,947), we examined the effect of patient characteristics and geographic regions on warfarin use.
  
  
  RESULTS
  The overall warfarin use rate was 66.8%. The warfarin use rates varied between hospital referral regions, with highest rates in the Midwestern states and lowest rates in the South. The regional variation persisted even after adjustment for patient characteristics. Multivariable analysis showed that the odds of being on warfarin decreased significantly with age and increasing comorbidity, in blacks, and among those with low income. Seeing a cardiologist (OR 1.10; 95% CI 1.05-1.16), having a PCP (OR 1.23; 95% CI 1.17-1.29), and CHADS(2) score of 2 or greater (OR 1.09; 95% CI 1.01-1.17) were associated with increased odds of warfarin use.
  
  
  CONCLUSIONS
  Warfarin use rates vary by patient characteristics and region, with higher rates among residents of the Midwest and among patients seen by cardiologists and PCPs. Preventing stroke-related disability in AF requires implementation of evidence-based initiatives to increase warfarin use.
authors: Division of Geriatrics; Department of Internal Medicine, Sealy Center on Aging, University of Texas Medical Branch (UTMB), Galveston, TX, USA. muraji@utmb.edu
authors: Mukaila A
authors: MA
authors: Raji
authors: Matthew
authors: M
authors: Lowery
authors: Yu-Li
authors: YL
authors: Lin
authors: Yong-Fang
authors: YF
authors: Kuo
authors: Jacques
authors: J
authors: Baillargeon
authors: James S
authors: JS
authors: Goodwin
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000150:complications / Q000188:drug therapy*; D015331:Cohort Studies; D019317:Evidence-Based Medicine / Q000379:methods; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D054524:Medicare Part D / Q000706:statistics & numerical data; D015999:Multivariate Analysis; D011320:Primary Health Care / Q000706:statistics & numerical data; D012189:Retrospective Studies; D012959:Socioeconomic Factors; D020521:Stroke / Q000209:etiology / Q000517:prevention & control*; D014481:United States; D014859:Warfarin / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D014859:Warfarin