The widely used blood thinner warfarin -- also known as Coumadin -- may raise the risk of severe bleeding inside the skull by much more than previously thought, a new study suggests.
Researchers examined data from nearly 32,000 U.S. veterans, aged 75 and older, with a common heart rhythm disorder called atrial fibrillation. The investigators found that almost one in three suffered an "intracranial" bleed while taking warfarin for the condition.
"Atrial fibrillation ("a-fib") is a common heart rhythm disorder in elderly patients. And in patients with a-fib, treatment with the blood thinner warfarin reduces the risk of stroke by nearly two-thirds," explained study lead author Dr. John Dodson.
"However, many clinicians are hesitant to prescribe warfarin in elderly patients, often because of concerns over head trauma due to falls, which can result in catastrophic bleeding," said Dodson. He is assistant professor of medicine at NYU Langone Medical Center in New York City.
Dodson noted that, until now, "no large study has looked at how common traumatic intracranial bleeding is in clinical practice, or if there are conditions that make patients higher risk."
To help find out, his team tracked outcomes between 2002 and 2012 for the population of elderly veterans, who all took warfarin for atrial fibrillation.
The study found that rates of traumatic intracranial bleeding among seniors with atrial fibrillation was higher than previously reported.
"Nearly one-third of patients experienced more than one episode of traumatic intracranial bleeding," Dodson pointed out, and many patients "also still experienced strokes during this time period."
The investigators also pinpointed several factors that raised bleeding risk: dementia, anemia, depression, use of anticonvulsant drugs, and highly variable levels of warfarin in the blood.
"These findings highlight the important balance between the benefits and risks of warfarin therapy in elderly patients with a-fib, and the need for a personalized approach," Dodson said.
Two experts agreed that finding the right balance -- between preventing clots but not raising bleeding rates -- has always been tough when it comes to treating atrial fibrillation.
"As the elderly population continues to grow, the incidence of conditions like atrial fibrillation also rises. And the mainstay of treatment continues to be blood thinners such as warfarin," said Dr. Richard Temes, director of the Center for Neurocritical Care at North Shore University Hospital in Manhasset, N.Y.
Temes said that newer (and much pricier) blood thinners -- drugs such as Eliquis, Pradaxa, and Xarelto -- have recently been developed, but come with their own problems. "As physicians, we need to carefully weigh the risks of using blood thinners in the elderly population, which is prone to falls and head injury, with the risks of stroke," he said.
Another expert agreed. "This article highlights a common problem facing the medical community -- the risks and benefits of anticoagulation in the elderly with atrial fibrillation, since this group has both a high risk of stroke and intracranial hemorrhage," said Dr. Joseph Germano, associate director of electrophysiology at Winthrop-University Hospital in Mineola, N.Y.
The study was funded by the U.S. National Institutes of Health and published online March 9 in the journal JAMA Cardiology.