Little Extra Bleed Risk With Warfarin in Elderly Patients

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Warfarin (Coumadin) "only mildly" increases bleeding risk after age 80, although the risk of thrombosis on the drug rises sharply after that age, a study showed.

Overall, in cohorts of patients in their 70s and in their 80s matched for vitamin K antagonist use duration to all 1,109 anticoagulant-prescribed patients age 90 and older at a single anticoagulation clinic in the Netherlands, major bleeding risk was not significantly different among the three groups.

The risk of any bleeding did rise modestly with age, Hilde A. M. Kooistra, PhD, of University Medical Center Groningen, the Netherlands, and colleagues reported online in JAMA Internal Medicine. Rates were:

• 14.8 per 100 patient-years among those ages 70 to 79
• 16.7 per 100 patient-years among those ages 80 to 89 (hazard ratio 1.07 vs their next younger counterparts, 95% CI 0.89-1.27)
• 18.1 per 100 patient-years among those 90 and older (HR 1.26 vs those in their 70s, 95% CI 1.05-1.50)

Thrombosis showed a more substantial difference within this understudied age group. The overall rate was 2.6%, with a 75% elevated risk for those in their 80s and 2.14-fold higher risk in those in their 90s and beyond (95% CI 1.22-3.75).

The poorer vitamin K antagonist control with rising age appeared to explain the increased bleeding risk in patients 90 years or older, but adjustment for the quality of control had little effect on the increased thrombosis risk for elderly individuals.

General lack of efficacy probably wasn't the reason, Kooistra's group suggested, rather, "physicians probably prescribed vitamin K antagonists to a selection of patients older than 80 years with a relatively high risk of thrombosis."

They concluded: "Our data suggest that the recommendations to use anticoagulants in patients older than 80 years can be safely extrapolated to the eldest patients as well, but evidence is stronger for women than for men," for whom the rise in bleeding risk was less steep with age.

Anna L. Parks, MD, and Kenneth E. Covinsky, MD, both of the University of California San Francisco, wrote in an accompanying editor's note, that these data are better than the extrapolated data and clinical experience that physicians have had to go on, but still only go so far:

"These data also suggest that clinicians are successfully identifying very old patients who can be given anticoagulation therapy with relative safety. However, we still know little about the patients who clinicians chose not to treat with anticoagulation therapy. Beyond absolute age, frailty, mobility problems, fall risk, and dementia influence decisions regarding anticoagulation therapy, and we need data on how these factors mediate risk of bleeding and thrombosis. We need more studies that include the very old and that measure the risk factors that are particularly relevant in the frail older population."

The researchers noted that their findings were likely generalizable from the perspective of having no exclusion criteria and no selection bias, as the thrombosis service managed anticoagulant therapy for all noninstitutionalized patients and the patients of many nursing homes in its geographic area, without any role in screening or selecting patients.