SAN FRANSICO—New research suggests bleeds and thrombosis are not the only adverse effects of improper warfarin dosing.
The study showed an increased risk of dementia among patients with atrial fibrillation whose warfarin doses were outside the therapeutic range for an extended period of time.
Jared Bunch, MD, of the Intermountain Medical Center Heart Institute in Murray, Utah, and his colleagues presented this finding at the 2014 Annual Heart Rhythm Society Scientific Session (PO05-169).
Previous research suggested that patients with atrial fibrillation had an increased risk of developing dementia. But the cause of that association
was unknown.
“[W]e now know that if warfarin doses are consistently too high or too low, one of the long-term consequences can be brain damage,” Dr Bunch said. “This points to the possibility that dementia in atrial fibrillation patients is partly due to small, repetitive clots and/or bleeds in the brain.”
To make this connection, the researchers analyzed data from 2693 atrial fibrillation patients receiving warfarin. The team evaluated the relationship between dementia and the percentage of time that patients’ warfarin doses were within the therapeutic range (international normalized ratio of 2 to 3).
In all, 4.1% of patients (n=111) were diagnosed with dementia. This included senile dementia (n=37, 1.4%), vascular dementia (n=8, 0.3%), and Alzheimer’s dementia (n=66, 2.4%).
The researchers’ analysis (adjusted for the risk of stroke and bleeding) revealed that the more time a patient’s warfarin dosages were outside the therapeutic range, the greater his risk of developing dementia.
Specifically, patients within the therapeutic range less than 25% of the time were 4.6 times more likely to develop dementia than patients within range more than 75% of the time.
Patients within the therapeutic range 25% to 50% of the time were 4.1 times more likely to develop dementia. And patients within the therapeutic range 51% to 75% of the time were 2.5 times more likely to develop dementia.
“Our results from the study tell us 2 things,” Dr Bunch said. “With careful use of anticoagulation medications, the dementia risk can be reduced.
Patients on warfarin need very close follow-up in specialized anticoagulation centers, if possible, to ensure their blood levels are within the recommended levels more often.”
“Second, these results also point to a potential new long-term consequence of dependency on long-term anticoagulation medications. In this regard, stroke prevention therapies do not require long-term anticoagulation medications, and reducing the use of these drugs will hopefully lower
dementia risk.”
