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Clinically significant bleeding occurs in 3.8% per year of pts aged 65+ years using warfarin

Clinical Question:
What are the real-world rates of hemorrage after the initiation of warfarin?

Bottom Line:
The risk of hemorrhage is 2.9% per person-year for patients aged 66 years to 75 years, and 4.6% per person-year for those older than 75 years. The risk is also higher for patients with a higher CHADS(2) risk score. It is important to keep this in mind when reading randomized controlled trials that report lower rates, which make the net benefit of anticoagulation appear more favorable than it probably is in the real world. (LOE = 2b)

Gomes T, Mamdani MM, Holbrook AM, Paterson JM, Hellings C, Juurlink DN. Rates of hemorrhage during warfarin therapy for atrial fibrillation. CMAJ 2013;185(2):E121-E127.  [PMID:23184840]

Study Design:
Cohort (retrospective)



In randomized controlled trials, the rate of major bleeding is typically between 1% and 3% per year. These patients are closely monitored and older patients are often excluded from these trials. These Canadian researchers linked pharmacy and hospital databases to identify patients older than 65 years with atrial fibrillation who initiated warfarin therapy over a 1-year period between 2007 and 2008. Then they determined each patient's CHADS(2) score, a measure of risk of venous thromboembolism (VTE) and any major bleeding episodes. The latter were defined as a visit to the emergency department or admission to the hospital for hemorrhage. The authors followed up the patients for up to 5 years, or until they stopped taking warfarin or had a hemorrhagic episode. The average age of patients in the cohort was 77 years, and a one third had a CHADS(2) score of 3 or higher. The risk of hemorrhage was highest in the first month of therapy (1% overall; 11.8% per person-year) and in patients with higher CHADS(2) scores. For example, patients with a CHADS(2) score of 4 or higher had a 6.0% risk per person-year, compared with 1.8% for those with a score of 2 or lower. The overall risk over the entire treatment period was 3.8% per person-year. This is higher than that reported by most studies, but somewhat lower than that seen in some other studies. The latter studies typically included shorter follow-up periods. Patients older than 75 years also had higher rates of hemorrhage than patients aged 66 to 75 years (4.6% vs 2.9%). Of patients admitted for hemorrhage, 1 in 5 died during or shortly after the hospitalization. One limitation is that the authors were unable to fully ascertain the use of aspirin or nonsteroidal antiinflammatory drugs because over-the-counter drug use is not tracked by the pharmacy database.


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