Atrial Fibrillation: Over/Under Anticoagulation Increases Risk of Dementia

Dr. T. Jared Bunch, M.D Medical Director for Heart Rhythm Services Intermountain Healthcare Interview with:
Dr. T. Jared Bunch, M.D
Medical Director for Heart Rhythm Services
Intermountain Healthcare network.

Medical Research: What is the background for this study? What are the main findings?

Dr. Bunch: Approximately 5 years ago we found that atrial fibrillation was associated with all forms of dementia, including Alzheimer’s disease.  At that time we did not know the mechanisms behind the association.  One hypothesis that we had was brain injury in patients with atrial fibrillation is in a spectrum, large injuries result in strokes and repetitive small injuries result in dementia.  In this regard, we anticipated that anticoagulation effectiveness and use may impact dementia risk.  Early this year we published in HeartRhythm Journal that atrial fibrillation patients with no history of dementia that have used warfarin, but had high percent times outside of the therapeutic range were much more likely to develop dementia.  We gained some insight from this trial in that we saw much higher risks of the patients were either over or under anticoagulated.

Amongst our atrial fibrillation patients using warfarin nearly one third are also taking aspirin, typically due to the presence of coronary artery disease or a prior myocardial infarction. We hypothesized since these patients were using two agents that increase risk of bleed that over anticoagulation with warfarin may be an even great risk for dementia.  This is was we found.  The patients over anticoagulated greater than 30 percent of the time were nearly 2 and a half times more likely to develop dementia compared to those that were over anticoagulated less that 10 percent to the time.

Medical Research: What should clinicians and patients take away from your report?

Dr. Bunch:

  • First, some people use aspirin believing it is heart healthy.  In these patients it should be stopped and only used in patients that have a clear need, such as preventing a second heart attack.
  • Second, in patients that require both agents, physicians need to be extra careful to educate and monitor them to minimize the time they spend over anticoagulated.
  • Finally, in those patients that consistently have marked variation in their warfarin levels, physicians should consider an alternative approach, although these have not been proven to reduce dementia.  However we have reason to hope the newer blood thinners will reduce dementia since they reduce strokes and large brain bleeds compared to warfarin.

Medical Research: What recommendations do you have for future research as a result of this study?

Dr. Bunch: We clearly need to study the new agents and their impact on cognition and dementia. We also need to look at other risk characteristics of bleeding risks in addition to aspirin that are very common and often progressive in atrial fibrillation patients such as kidney dysfunction.

Citation: AHA14 abstract

Long-term overtreatment with anti-clotting/antiplatelet drug combo may raise risk of dementia