Among warfarin users, patients with AF at increased risk for dementia

SAN FRANCISCO — In patients taking warfarin long term, those with atrial fibrillation had elevated risk for dementia, according to a presentation at the Heart Rhythm Society Annual Scientific Sessions.

“First, as physicians we have to understand that although we need to use anticoagulants for many reasons including to prevent stroke in AF patients, at the same time there are risks that need to be considered, some of which we are only beginning to understand,” T. Jared Bunch, MD, director of heart rhythm research at Intermountain Medical Center Heart Institute, Salt Lake City, medical director for heart rhythm services for the Intermountain Healthcare system and lead author of the study, said in a press release. “In this regard, only those that absolutely need blood thinners should be placed on them long term.”

T. Jared Bunch

Although mechanisms behind the association between dementia and AF are unknown, researchers found previously an increased risk for patients with AF to develop dementia when treated with warfarin with low percentage of time in therapeutic range (TTR) compared to patients that had high percent TTR. The higher risk of dementia with low percentage TTR was most pronounced in younger AF patients. These prior studies established a background that efficacy of anticoagulation was important in long-term cognitive function. However, the extent to which AF might increase risk for dementia beyond long-term exposure to anticoagulation was unknown.

The study, which was conducted by the Intermountain Healthcare Clinical Pharmacist Anticoagulation service, enrolled 10,537 patients aged 18 years or older with no history of dementia who were undergoing long-term treatment with warfarin for AF and non-AF conditions, primarily heart valves or history of recurrent thromboembolism. Study variables included age, hypertension, renal failure, prior MI, heart failure, cerebrovascular accident, smoking history, hyperlipidemia and diabetes; patients with AF had higher rates of hypertension, heart failure, diabetes and stroke than patients without it.

After follow-up of approximately 7 years, Bunch and colleagues found that all types of dementia increased in patients with AF more than in patients without it that used warfarin anticoagulation for other reasons. Compared with those without AF, patients with AF had higher rates of total dementia (5.8% vs 1.6%, P < .0001), Alzheimer’s disease (2.8% vs 0.9%, P < .0001) and vascular dementia (1% vs. 0.2%; P < .0001), according to the researchers.

Regarding long-term anticoagulation exposure, regardless of reason for taking warfarin, dementia rates increased in an incremental manner when warfarin levels were regularly out of therapeutic range.

In order to account for broad differences in baseline cardiovascular risk factors between AF and non-AF anticoagulated patients, researchers conducted a propensity-matched analysis of 6,030 patients. In this matched analysis, the elevated risk for dementia in those with AF remained (total dementia: HR = 2.42; 95% CI, 1.85-3.18; Alzheimer’s disease: HR = 2.04; 95% CI, 1.4-2.98; senility: HR = 2.46; 95% CI, 1.58-3.56).

“Our study results are the first to show that there are significant cognitive risk factors for patients treated with warfarin over a long period of time regardless of the indication for anticoagulation. Nonetheless, this study does highlight the fact that atrial fibrillation conveys an added risk and as such this finding may be used to look at strategies to lower dementia rates in these patients” Bunch said in the release. – by Dave Quaile

Reference:

Bunch TJ, et al. Session MP01. Presented at: Heart Rhythm Society Scientific Sessions; May 4-7, 2016; San Francisco.

Disclosure: Cardiology Today could not obtain relevant financial disclosures.