Anticoagulants are the cornerstone of stroke prophylaxis in patients with atrial fibrillation (AF), a condition that disproportionately affects individuals as they age.1 Since older age is a risk factor for bleeding as well as thrombosis, weighing the risks and benefits of anticoagulants—which increase bleeding risk—is essential.1

Indeed, determining which older patients should receive anticoagulation therapy is “one of the most fraught choices clinicians make.”2

Underuse of Anticoagulants in the Elderly

Clinicians are frequently reluctant to prescribe vitamin K antagonists (VKAs) for anticoagulation in the elderly due to concerns about increased bleeding risk.3

“I have seen this problem in my own practice,” Anne B. Curtis, MD, told Cardiology Advisor.

“Of the patients who come to see me for second opinions, the ones most likely to be on anticoagulation are the younger patients in their 50s, not the ones in their 80s,” said Dr Curtis, professor and chair, Jacobs School of Medicine and Biological Sciences Department, University of Buffalo in New York. The fear may be disproportionate, she said.

Investigating Bleeding Risk

Several studies have demonstrated that patients older than 80 years of age with venous thromboembolism (VTE) are at greater risk of death from recurrent VTE than from fatal bleeding while taking a VKA, and that patients older than 75 can benefit from anticoagulant therapy.4,5 But can these findings be extrapolated to patients older than 90?

A recent Dutch study3 investigated VKA-associated risks in elderly patients being treated in a thrombosis service. The researchers randomly matched 1109 patients, aged 90 years or older, with 1100 patients aged 80 to 89 years and 1104 patients aged 70 to79 years.  The primary outcome was a composite of clinically relevant non-major and major bleeding. Secondary outcomes included thrombosis and quality of VKA control.

The researchers found that the risk of bleeding was not significantly increased in patients aged 80 to 89 years and only mildly increased in patients 90 years or older, as compared with patients aged 70 to 79 years. On the other hand, risk of thrombosis was higher for patients in their 90s and 80s than for patients in their 70s.

In an accompanying editorial,2 Drs Parks and Covinsky noted that the study “offers valuable information on real-world outcomes” and suggests that clinicians are “successfully identifying very old patients who can be given anticoagulation therapy with relative safety.”

However, the authors warned, “We still know little about the patients who clinicians chose not to treat with anticoagulation therapy” because they were not included in the study.

In an interview with Cardiology Advisor, Kenneth Covinsky, MD, MPH of the UCSF Division of Geriatrics in San Francisco, expanded on his editorial.“The study was convincing that there are patients age[d] 90 [years or older] who can be treated safely with anticoagulants. But who are these patients? What factors determine whether an elderly patient is a candidate for this treatment?”

“We are still in an evidence-free zone,” he commented.

Special Concerns in the Elderly

Dr Curtis remarked that the study findings support her own views and practice, adding that clinicians must still be attentive to “special concerns that increase with age, such as comorbidities and polypharmacy.”

Polypharmacy is rampant among elderly people, she noted, with some taking as many as 6 to 8 medications.6 Many commonly used drugs are contraindicated in patients taking VKAs—eg, certain antibiotics (such as penicillin and quinolones), amiodarone, nonsteroidal antiinflammatory drugs (NSAIDs), and certain lipid-lowering agents.7 Additionally, VKAs can interact negatively with many foods, Dr Curtis pointed out.

For this reason, the decision whether or not to prescribe VKAs sometimes depends on non-clinical factors, Dr Covinsky said. “Is the patient cognitively impaired? Does he or she have a caregiver administering or monitoring the medication? Does the patient understand and adhere to dietary restrictions? Is the patient a fall risk?”

Dr Curtis does not feel that cognitive impairment, per se, should disqualify a patient from use of anticoagulants. “If a patient cannot self-administer one drug, chances are he or she cannot self-administer other drugs either, and the concern therefore applies to all drugs and the need for a caregiver.”

The focus on potential bleeding as a result of falls—which is the most common reason for not prescribing warfarin to elderly patients with AF8—may be overstated, Dr. Curtis said, citing data suggesting that a patient would have to fall more than 200 times9 to “tip the risk/benefit analysis in favor of fall risk.”

Minimizing a patient’s fall risk can be accomplished via close monitoring of INR, environmental changes, management of all medications the patient is taking, and treatment of underlying diseases that might contribute to impaired stability.10,11 It can be helpful to use a fall risk calculator.12

Competing Risks

Margaret Fang, MD, associate professor, UCSF School of Medicine, San Francisco, told Cardiology Advisor that the concept of “competing risk” plays an important role in the decision-making process. “We know the risk of stroke increases with age, but the risk of dying from other causes, such as cancer or infection, increases at an even faster rate.”