After age 80, the bleeding risk with a vitamin K antagonist (VKA) only mildly increases whereas the thrombosis risk in this patient population sharply increases, a study in JAMA Internal Medicine reports.

Earlier studies have demonstrated that even with an increased risk of bleeding, elderly patients still benefit from taking anticoagulants if they have a strict indication. Many of these studies only include a small number of patients >90 years old so it is not clear whether this benefit extends to the eldest population group. 

Researchers from The Netherlands aimed to assess the risk of bleeding and thrombosis associated with age in patients aged >70 years who were treated with a VKA. They performed a matched cohort study of patients treated with a VKA between January 21, 2009–June 30, 2012. A total of 1,109 patients aged ≥90 years treated with a VKA were matched with 1,100 patients aged 80–89 years and 1,104 patients aged 70–79 years based on duration of VKA treatment. The primary outcome measure was a composite of clinically relevant non-major and major bleeding; secondary outcomes included thromboses and quality of control. 

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Over the 6,419 observation-years, 713 of the 3,313 patients experienced 1,050 bleeding events. The risk of bleeding was not significantly increased in patients aged 80–89 years (event rate per 100 patient-years [ER] 16.7, hazard ratio [HR] 1.07, 95% CI: 0.89–1.27) and mildly increased in patients aged ≥90 years (ER 18.1, HR 1.26, 95% CI: 1.05–1.50) vs. patients aged 70–79 years (ER 14.8). 

Compared with those aged 70–79 years (ER 0.9), the point estimates for major bleeding (including fatal bleeding) were similar for those aged 80–89 years (ER 1.0, HR 1.09, 95% CI: 0.60–1.98) and those aged ≥90 years (ER 1.1, HR 1.20, 95% CI: 0.65–2.22). The increase in bleeding risk was steeper for male patients vs. female patients, the study authors reported. 

The risk of thrombosis was greater in patients in their 90s (HR 2.14, 95% CI: 1.22–3.75) and 80s (HR 1.75, 95% CI: 1.002–3.05) vs. patients in their 70s. VKA control worsened with age, which partially explained the increased bleeding risk in those older than 90, however the increased thrombosis risk was not mediated by VKA control.

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