Delayed Anticoagulation Linked to Dementia Risk in AF

 Fran Lowry

May 13, 2017

CHICAGO, IL — Delaying use of anticoagulation therapy with warfarin beyond 30 days after the initial diagnosis of atrial fibrillation (AF) is associated with a significant increase in the risk of dementia over time, according to a new study[1].

"Unfortunately, the majority of patients who are started on warfarin are started more than 30 days after their initial diagnosis of AF," lead author Dr T Jared Bunch (Intermountain Health Care, Salt Lake City, UT) told heartwire from Medscape.

"The risks of dementia continue to rise as delays in starting warfarin increase," Bunch said.

He presented the results of this observational study here at the Heart Rhythm Society (HRS) 2017 Scientific Sessions.

Physicians are often reluctant to start their AF patients on warfarin, and patients are often hesitant about what they associate with rat poison, Bunch said.

"Warfarin can be a difficult drug to start. It takes routine blood monitoring, and there are frequent drug-to-drug and drug-to-food interactions that change the levels," Bunch said.

What often ends up happening is that physicians and their patients opt for an "easier" route and start antiplatelet therapy with aspirin, but this is not the approach to take, Bunch noted.

"The general perception with aspirin is that it's a heart-healthy therapy. Unfortunately, aspirin has never been proven to reduce stroke in patients with atrial fibrillation, whether they are low-risk or moderate- to high-risk patients. There is no benefit at all," he added. "In fact, we found a slight trend toward increased risk of dementia in delaying aspirin use, but even starting aspirin within 30 days, the dementia rates were still higher than what we would see in those who were treated with warfarin right away."

Bunch and his team studied 26,189 patients with AF, no history of anticoagulation use at diagnosis, and no history of dementia.

Of these, 21,781 patients were subsequently treated with antiplatelet agents (aspirin and clopidogrel) and 4408 were subsequently treated with warfarin.

The average age of the patients was 69.2 years and 56.8% were male. Risk factors included hypertension (55.2%), diabetes (21.5%), heart failure (23.3%), and prior stroke/transient ischemic attack (TIA) (6.2%).

The study's primary end point was incident dementia at the following time points: ≤30 days, 31 days to 1 year, >1 year to 3 years, and >3 years.

Of the patients receiving antiplatelet therapy with aspirin and clopidogrel, 48% were started within 30 days of their initial AF diagnosis and 28.4% were started on antiplatelet therapy 3 years or more after their diagnosis.

Of the patients receiving warfarin therapy, just 5.2% were started within 30 days of their diagnosis and 65.3% of patients were started on warfarin more than 3 years after their diagnosis.

Rates of dementia began to rise at all time points, with longer delays in starting anticoagulant treatment associated with a greater risk of dementia.

Patients prescribed aspirin and clopidogrel 3 years or more after their initial diagnosis had a more than threefold increase in the risk of dementia (hazard ratio [HR] 3.39, 95% CI 2.4–4.65; P<0.0001).

Similarly, delays in warfarin therapy were associated with a two-and-a-half times greater risk of developing dementia (HR 2.55, 95% CI 1.59–4.09; P<0.0001).

Delays in Warfarin Therapy Common

"I think our study highlights important findings for clinicians," said Bunch.

"Delays in warfarin use are extremely common in the healthcare system. Unfortunately, even more common is just general underuse of anticoagulants. Even in people who are at high risk and who have experienced a prior stroke or TIA, the use of warfarin is still very inconsistent. Depending on the group you look at, anywhere from 30% to 50% of people who should be on blood thinners are not."

Bunch added that he thinks clinicians will be more likely to start their newly diagnosed AF patients on the newer anticoagulants earlier.

"We didn't look specifically at the newer anticoagulants in this study because we don't have enough follow-up time, but we would anticipate that the new anticoagulants, which are more predictable, have a quicker onset of action, and have less drug-to-drug and drug-to-food interactions, may perform even better than warfarin.

"That said, it's going to be tough to beat warfarin started immediately," he added. "Our dementia rates are almost zero if warfarin is started quickly."

The study was supported by Intermountain Health Care Heart Institute. Bunch reported no relevant financial relationships.

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