A matched cohort study of older adults who received a vitamin K antagonist found that the risk of bleeding did not significantly increase as patients entered their 80s and only mildly increased they entered their 90s.

However, the risk of thrombosis in patients who were in their 80s and 90s was higher and more often fatal compared with patients in their 70s.

Lead researcher Hilde A. M. Kooistra, PhD, of the University Medical Center Groningen in the Netherlands, and colleagues published their results online in JAMA Internal Medicine on July 5.

For this analysis, the patients evaluated 1,109 patients who were 90 years or older and were treated with a vitamin K antagonist between Jan. 21, 2009, and June 30, 2012, at Certe Thrombosis Service Groningen in the Netherlands.

The patients were then randomly matched in a 1:1:1 ratio with 1,100 patients between 80 and 89 years old and 1,104 patients between 70 and 79 years old based on their duration of vitamin K antagonist treatment.

The bleeding event rate was 14.8 per 100 patient-years in the 70 to 79 year old group, 16.7 per 100 patient-years in the 80 to 89 year old group and 18.1 in the 90 and older group.

Patients who were 90 or older had a 26 percent increased risk of bleeding compared with patients in their 70s, while patients in their 80s had a 7 percent increased risk of bleeding compared with patients in their 70s.

The event rate of major bleeding was 0.9 per 100 patient-years in the youngest group, 1.0 per 100 patient-years in the middle group and 1.1 per 100 patient-years in the oldest group.

The point estimates for major bleeding were similar between the groups, according to the researchers. They added that men had an increased risk of bleeding compared with women.

The event rate of thrombotic events was 0.8 per 100 patient-years in the youngest group, 1.5 per 100 patient-years in the middle group and 1.8 per 100 patient-years in the oldest group. The risk of developing thrombosis was significantly higher among patients in their 80s and 90s versus patients in their 70s.

The researchers said the increased risk of bleeding in patients in their 90s was partly explained by their poorer control of vitamin K antagonists. However, they said that the increased risk of thrombosis was not due to control of vitamin K antagonists.

They also cited a few limitations of the study, including that they did not enroll patients with a high risk of bleeding who were ineligible to use anticoagulants. They also excluded patients who initiated vitamin K antagonist therapy but died before their first appointment. In addition, they did not specify the cause of some strokes.

They mentioned a few strengths of the study, as well, including the use of real-life data, the thorough adjudication of end points and the large cohort size.

“Irrespective of the underlying mechanism, our data on patients considered eligible for anticoagulation therapy suggest that the recommendations to use anticoagulants in patients older than 80 years can be safely extrapolated to the eldest women as well,” they wrote. “The stronger increase in risk of bleeding in the eldest men makes us more cautious to draw final conclusions for this group of patients.”