The incidence of dementia diagnosed by a consultant neurologist during follow-up was 5.8% in the group with an INR above 3.0 at least 25% of the time, more than twice the 2.7% rate in patients with a high INR less than 10% of the time. In the middle group, the incidence of dementia was 4.1%. In a multivariate Cox regression analysis, having an INR above 3.0 on at least 25% of occasions was independently associated with a 2.59-fold increased risk of developing dementia, making it by far the most potent risk factor in their analysis.
The next step in their research will be to perform serial brain imaging and volumetric scans, Dr. Bunch said. Also, he and his coworkers are 3 years into an ongoing study looking at the incidence of dementia in AF patients on the various novel oral anticoagulants, where INR is a nonissue. Their hypothesis is the dementia risk will be lower than in patients on warfarin. Dr. Bunch has particularly high hopes for AF patients on apixaban (Eliquis) because it’s known to have a reduced risk of large bleeds, stroke, and GI bleeding; the hope is it will cause fewer cerebral microbleeds as well.
In an interview, the cardiologist said he believes his study showing an increased risk of dementia in AF patients with supratherapeutic INRs on warfarin plus antiplatelet therapy holds several important lessons for AF patients and physicians alike.
For patients, the message is don’t just start taking aspirin on your own because you’ve read it’s good for your heart or may reduce cancer risk; consult your physician.
And for physicians, it’s important to ask all patients on warfarin if they’re using aspirin; many don’t ask. Also, periodically reconsider the need for dual therapy with warfarin and aspirin.
“We find the risks of stroke and bleeding change dynamically over time, so the initial therapy for stroke prevention may not be the ideal therapy after 5-10 years,” Dr. Bunch said.
Lastly, for patients who are overanticoagulated on a substantial percentage of their INR measurements, it’s essential to consider a change in strategy. Either follow their INRs more closely and adjust warfarin dosing accordingly, or switch to one of the novel, more predictable oral anticoagulants, he concluded.
This study was funded internally by Intermountain Healthcare. Dr. Bunch reported having no financial conflicts.