Atrial Fibrillation and the Link to Dementia


AFib is a complication where the heart can beat too fast, too slow, or with an irregular rhythm. AFib is the most common type of arrhythmia encountered in clinical practice and its prevalence increases with age, sedentary lifestyles, and obesity. Dementia in general, is a term for a decline in mental ability severe enough to interfere with daily life.

“The combined disease state is associated with significantly higher risk of mortality,” said Dr. Bunch.

Both diseases are at epidemic levels in the U.S. and climbing globally. The Centers for Disease Control and Prevention (CDC) estimate 2.7 – 6.1 million people in the United States have AFib.  The disease affects more women than men because they live longer on average. Dementia also strikes more women than men and has now become the leading killer of women, causing three times as many deaths than breast cancer. Due to the epidemic levels, it has become urgent to understand the mechanisms between both diseases and to optimally treat both.

A study by Dr. Bunch, principal investigator and other researchers at the Intermountain Medical Center Heart Institute in Murray, Utah, found that AFib patients who are on blood thinning medications are at higher risk of developing dementia if their doses are not in the optimal recommended range. A study of more than 2,600 AFib patients found they are significantly more likely to develop dementia when using medicines to prevent blood clots when their dosing is too high or too low for an extended period.

Physicians try to achieve a ratio within the therapeutic range, or the safety range. Typically, dosages higher than the therapeutic range can increase the risk of bleeding. If the dose is lower than the therapeutic range, it can increase risk of blood clots forming.

 “Most patients who develop atrial fibrillation require the use of an anticoagulant to prevent a stroke. The most common anticoagulant used worldwide is warfarin, and we now know that if warfarin doses are consistently too high or too low, one of the long-term consequences can be brain damage,” said Dr. Bunch. “This points to the possibility that dementia in atrial fibrillation patients is partly due to small repetitive clots and/or bleeds in the brain.”

Researchers collected results from the same study with 4 percent of them having been diagnosed with dementia. Results were based on the percentage of time their blood-thinning medications were within the range. The more time their dosages were within the range, the less risk they had of developing dementia.


  • Patients within the therapeutic range less than 25 percent of the time were 4.5 times more likely to develop dementia.
  • Patients within the therapeutic range 25-50 percent of the time were 4.1 times more likely to develop dementia.
  • Patients within the therapeutic range 51-75 percent were only 2.5 percent more likely to develop dementia.

An anticoagulation strategy can influence risk of dementia development in AFib patients. Genetic markers of arrhythmia and stroke risk are also associated with increased risk of dementia.