If you have atrial fibrillation and are on warfarin (Coumadin, Jantoven), keeping your blood levels within an ideal range may help you do more than avoid stroke, one of the major risks of having atrial fibrillation.
Keeping your warfarin blood levels in a target range may also help protect you from dementia, according to new research.
The link between afib and Alzheimer's disease, the most common form of dementia, has been known for a few years, says T. Jared Bunch, MD, Everyday Health columnist, cardiologist at Intermountain Heart Institute, and Medical Director for Cardiac Electrophysiology at Intermountain Health Care in the Salt Lake City area.
His team has found that maintaining target blood levels of your anticoagulant (i.e. Coumadin, warfarin) can help preserve cognitive functioning.
"What we found was, there was a very significant correlation with the lack of Coumadin effectiveness, or lower percent of times in the therapeutic range, and the risk of dementia," Bunch says.
The study, published August 2014 in Heart Rhythm included 2,600 patients. Their average age was 74. None had dementia at the study start. But by the end of the five-year follow up, 109 patients had been told by a neurologist that they had dementia.
Next, Bunch's team looked to see if there was any link between two things — how often these patients with atrial fibrillation had their warfarin within the ideal target range, and whether or not they developed dementia. He used the standard ideal target range, an INR (international normalized ratio) of 2 to 3.
Better Target Range, Less Dementia Risk
The study found a strong link with the amount of time a patient’s INR was in a target range and the likelihood of developing dementia. While this can't prove cause and effect, the researchers did find a strong correlation. Those who had an INR in the target range (2 to 3) more than 75 percent of the time — were four times less likely to develop dementia than those in the target range only 26 to 50 percent of the time.
"What we found is, if you can have a reliable, predictable level of Coumadin in the blood, the risk of dementia is quite low," Bunch says. He followed the patients for five years, and then did an estimate or projection for an entire decade. "From the data, the projected risk of dementia with very well-controlled Coumadin was less than 3 percent at 10 years," Bunch says.
He found an increased risk of dementia not just when blood levels were below the target. There was also a suggestion of increased risk when the blood level is too high, particularly in patients over 80 yrs old. If the blood level is too low, there is a danger of developing blood clots, which increase the risk of strokes, experts know. However, if blood levels are too high, there can be brain bleeds, which can also compromise the brain.
"The study doesn't suggest we need more blood thinning," Bunch says, "but that we need more effective blood thinning."
Warfarin Levels & Dementia: Second Opinion
The new findings definitely suggest that keeping warfarin within the ideal range provides dementia protection as well as stroke protection, says Luigi Di Biase, MD, PhD, senior researcher at the Texas Cardiac Arrhythmia Institute, St. David's Medical Center, Austin. He reviewed the findings.
"It makes absolute sense," he says. However, he concedes, it can be difficult for patients with atrial fibrillation to stay in that optimal range. This is because warfarin can interact with other drugs. And certain foods and drink (greens, alcohol) can affect how well warfarin works.
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Best Advice for Atrial Fibrillation Patients
Bunch can't yet say if the findings about dementia protection apply to the newer generation anticoagulants, the alternatives to warfarin. His team only studied warfarin.
"We don't quite know if the [findings] will be translatable," Bunch says. The newer anticoagulants include dabigatran (Pradaxa), rivaroxaban (Xarelto) and apixaban (Eliquis). One of their major selling points is the lack of a need for blood testing, although the ideal monitoring schedule is under some debate.
"The novel agents do not require frequent monitoring," Bunch says. "There is not a blood test that is commercially available that measures their effectiveness in the blood." He typically monitors kidney function with a blood test twice a year in his patients taking these newer drugs. "We do this because the drug elimination is greatly influenced by changes in kidney function, and if we see a decline, we lower the dose."
The newer anticoagulants are safer in regards to bleeds in the brain, Bunch says, and all lower stroke risk. In general, patients find it easier to maintain target blood levels on the newer drugs, he says.
Until more research is in, you can take steps to improve your health, no matter which drug you are taking for atrial fibrillation, Bunch says. His tips:
- If you are just starting on an anticoagulant, develop a monitoring plan with your health care provider, and stick to it.
- If your blood level of the anticoagulant is not ideal 75 percent of the time, ask your doctor if you should switch to another drug to see if it might work better.