The research was conducted by a team of investigators from the University of California, San Francisco, Massachusetts General Hospital, the Division of Research at Kaiser Permanente, and Boston University School of Medicine.
Using a sample of 13,559 patients with atrial fibrillation, which is rapid irregular contractions of the heart, researchers examined how rates of major hemorrhage changed with age. They found older age is an independent risk factor for developing bleeding in the body, and in particular bleeding in the brain, known as intracranial hemorrhage. Their findings are reported in the August 10 issue of the Journal of the American Geriatrics Society.
Atrial fibrillation is the most common cardiac arrhythmia and a major risk factor for stroke. Prior studies have shown that anticoagulation medication , such as warfarin, substantially reduces the risk of atrial fibrillation-related stroke, but also increases the risk for hemorrhage.
"Our findings show that although older patients have a greater risk for hemorrhage, the overall likelihood of hemorrhage on warfarin is relatively small, especially when one considers the benefits of stroke prevention," said lead author Margaret Fang, MD, MPH, assistant professor of medicine and hospitalist at UCSF Medical Center. "Carefully monitored warfarin therapy can be used with reasonable safety in older patients."
The study patients were followed for an average of 2.4 years. Findings showed 170 patients suffered major hemorrhages while taking warfarin compared to 162 patients not taking warfarin. Overall, patients on and off warfarin had less than a 0.5 percent chance of suffering an intracranial hemorrhage, the most destructive form of hemorrhage. According to the research, the risk of hemorrhage rose with older age regardless of therapy, but overall rates of hemorrhage were still quite low.
"An important finding of this study is that the rates of intracranial hemorrhage rose at age 80 and older," said Fang. "This link shows that regardless of therapy, physicians should be especially vigilant in monitoring patients over age 80 with atrial fibrillation."
The researchers also found that in addition to older age, prior gastrointestinal hemorrhage, anemia, renal insufficiency, hypertension and coronary disease were also risk factors for hemorrhage.
"The low rates of hemorrhage in our study show that clinicians may safely prescribe warfarin for many older patients with atrial fibrillation," Fang said. "However, they should take care to minimize modifiable risk factors for hemorrhage, such as excessively high anticoagulant intensities."
The researchers used data from Kaiser Permanente's AnTicoagulation and Risk Factors In Atrial Fibrillation (ATRIA) Study cohort.