BARCELONA (FRONTLINE MEDICAL NEWS) – The risk of developing dementia was reduced by 48% in patients with atrial fibrillation who were adherent to oral anticoagulation compared with those who were not, according to a Swedish propensity-matched registry study involving nearly 162,000 patients with the arrhythmia.

The study also addressed whether patients with atrial fibrillation (AF) are better off in terms of reducing their dementia risk if they’re on warfarin versus one of the novel oral anticoagulants. The answer is that it makes absolutely no difference, Leif Friberg, MD , reported at the annual congress of the European Society of Cardiology.

“We found no difference whatsoever in any of the subgroups. It appears that it is more important that you have some kind of oral treatment than exactly what kind to have,” said Dr. Friberg, a cardiologist at the Karolinska Institute in Stockholm.

It’s well established that AF is associated with increased risk of dementia, presumably because the arrhythmia kicks out microemboli that get distributed throughout the brain. But it has been unclear whether oral anticoagulation (OAC) prescribed for stroke prevention has the side benefit of reducing the elevated dementia risk.

“A randomized, controlled trial would be ideal to look at this, but it would be impractical and unethical. Second best [would be] a registry study with propensity matching,” according to Dr. Friberg.

And that’s just what he and his coinvestigators carried out. The study included 80,948 AF patients with no baseline diagnosis of dementia who were prescribed an OAC and an equal number of propensity-matched, dementia-free AF patients not on OAC therapy. During up to 8 years of follow-up, the unadjusted risk of a new diagnosis of dementia was 29% lower in the group on an OAC at baseline.

But the Swedish registries also enabled investigators to zero in on the impact of OAC in patients who were actually medication adherent over time. Dr. Friberg and his coworkers identified a subgroup of 50,406 AF patients who regularly filled their OAC prescriptions and took the medication at least 80% of the time, as well as 48,947 propensity-matched controls who never used OACs. In this on-treatment analysis, the OAC users had a robust 48% relative risk reduction in new diagnosis of dementia. The dementia curves diverged almost immediately and the gap between the two curves continued to widen throughout follow-up. All examined subgroups benefited, regardless of age, gender, AF duration, CHA2DS2-VASc score, or the presence or absence of diabetes, renal failure, or frequent falling.

“This is an important issue,” Dr. Friberg declared. “You may say, ‘What do we care about these findings? These patients are all supposed to be on an oral anticoagulant anyway.’ But you know, patients stop taking their oral anticoagulant. We’re pretty good at initiating treatment when we meet patients for the first time, if they have stroke risk factors, but annually, 10%-15% of patients drop out of treatment. And if patients aren’t concerned enough about their risk of stroke, they might be more concerned about the risk of becoming demented. So these data provide an additional argument for the need to persevere with oral anticoagulation therapy.”

Session cochair Gabriel Tatu-Chitoiu, MD , was skeptical.

“I’ve been working in the atrial fibrillation field for 40 years, and I have to say I haven’t seen a strong dementia possibility in my patients,” said Dr. Tatu-Chitoiu, a cardiologist in Bucharest, Romania, and immediate past president of the Romanian Cardiology Society.

Dr. Friberg replied that AF patients are elderly, and many of them may stop going to their cardiologist when they develop dementia.

“I don’t think you can make extensions from personal experience on this. You have to trust in statistical evidence,” he observed.

Dr. Friberg reported receiving research funding from Bayer, Bristol-Myers Squibb, Pfizer, and Sanofi. However, the registry study was carried out without commercial support.