medwireNews: Very elderly patients given a vitamin K antagonist (VKA) in clinical practice have a mildly elevated risk of bleeding but a sharply increased risk of thrombosis, say researchers.
They report that the overall bleeding rates per 100 patient–years were 14.8 among 1104 patients aged 70–79 years, 16.7 among 1100 aged 80–89 years and 18.1 among 1109 aged 90 years or older.
The patients were treated at a single centre between 2009 and 2012. Their corresponding major bleeding rates were 0.9, 1.0 and 1.1 per 100 patient–years and intracranial bleeding rates were 0.5, 0.4 and 0.3 per 100 patient–years.
After matching the patients based on whether they had recently started VKA therapy or had been taking it long term, the team found the overall risk of bleeding was elevated a significant 1.26-fold among patients in the oldest versus the youngest age groups, but was not increased in the intermediate age group.
Gender also played a role. Hilde Kooistra (University Medical Center Groningen, the Netherlands) and study co-authors found that bleeding risk was not increased in women of any age, whereas men tended to have an increased risk in the intermediate age group and had a significant 1.71-fold increase at the oldest ages.
This “makes us more cautious to draw final conclusions for this group of patients”, the team writes in JAMA Internal Medicine.
In contrast with bleeding rates, the rate of thrombotic events rose sharply with advancing age, from 0.8 per 100 patient–years in the 70–79-year age group to 1.5 and 1.8 per 100 patient–years among patients aged 80–89 years and 90 years or older, respectively. This equated to significant 1.75- and 2.14-fold increases in the intermediate and oldest age groups, respectively.
Older patients newly starting VKA therapy had the highest thrombotic risk, with both the intermediate and oldest age groups having about a fivefold increased risk relative to the youngest age group.
The researchers doubt that the high thrombotic risk was due to lack of VKA efficacy, suggesting instead that “physicians probably prescribed VKAs to a selection of patients older than 80 years with a relatively high risk of thrombosis.”
In an editor’s note, Anna Parks and Kenneth Covinsky, from the University of California, San Francisco, USA, say 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, they note that “we still know little about the patients who clinicians chose not to treat with anticoagulation therapy”.
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