Long-term exposure to excess anticoagulation and platelet inhibition increases dementia risk

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

News - Nov. 20, 2014

Presented at the AHA Scientific Sessions 2014 by: Thomas Bunch (Intermountain Medical Center Cardiology, Eccles Outpatient Care Center Murray, UT)


Patients with atrial fibrillation (AF) have a higher risk of developing all forms of dementia. It is unknown which mechanism underlies this association. It is possible that exposure to chronic microbleeds results in repetitive cerebral damage which manifests as cognitive decline.
This study tested the hypothesis that AF patients who receive antiplatelet therapy, have more dementia if this is coupled to a greater part of the time exposure to over-anticoagulation.
1031 Chronically anticoagulated patients on warfarin, with target INR 2-3 and who were monitored by an Anticoagulation Service, were included, without a history of dementia or stroke/TIA, and who were receiving antiplatelet therapy. Dementia was estimated based on neurologically determined ICD-9 codes.

Main results

  • Dementia was diagnosed in 2.7% of patients with 25% supratherapeutic INR levels (n=240).
    Patients with longer than 25% of time supratherapeutic INR levels had a higher risk of dementia during follow-up.
  • After multivariate correction patients with over 25% of time supratherapeutic INR showed a higher frequency of dementia as opposed to those in whom that was the case <10% of time (HR: 2.40, P=0.04).


In patients who received both anticoagulation and antiplatelet therapy, the percentage of time that they were exposed to excess anticoagulation is related to the risk of dementia. These results point towards chronic brain damage due to microbleeds; a potential mechanism underlying the association between AF and dementia.

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