There is a higher incidence rate of intracranial bleeding than previously thought, in older patients who initiate warfarin therapy for atrial fibrillation (AF), suggesting that greater individual factors should be discussed with patients before warfarin administration begins.

Those are the findings of a new study, the largest to date, that evaluated the level of intracranial bleeding in adults (>75 years) who initiate warfarin therapy. Warfarin treatment can significantly reduce the risk of stroke for patients with AF, though half of the eligible older adults with AF are not given the treatment due to potential adverse events. These include fall risks and subsequently the possibility of intracranial bleeding.

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The researchers conducted a retrospective cohort study of 31,951 Veterans Affairs (VA) patient records, over the age of 75-years, with a median age of 81.1. The primary outcome was hospitalizations either within VA hospitals or at outside hospitals. Secondary outcomes included (1) hospitalization for any intracranial bleeding (traumatic or nontraumatic) and (2) hospitalization for ischemic stroke.

After a median follow-up time of 2.97 years, results showed the rate of traumatic intracranial bleeding was 4.80 per 1000 person-years. The absolute event rates for traumatic intracranial bleeding were 0.54% at 1 year and 2.10% at 3 years. Significant risk factors for traumatic intracranial bleeding included dementia (HR, 2.11; 95% CI, 1.53-2.92), as well as fall within the past year (HR, 1.72; 95% CI, 1.21–2.44); anemia (HR, 1.35; 95% CI, 1.10–1.65); depression (HR, 1.49; 95% CI, 1.22–1.82); abnormal renal or liver function (HR, 1.42; 95% CI, 1.00–2.01); anticonvulsant use (HR, 1.30; 95% CI, 1.01–1.69); and labile INR (HR, 1.40; 95% CI, 1.10–1.80).

For the secondary outcomes, for any intracranial bleeding the incidence rate was 14.58 per 1000 person-years. Fifty-seven percent of these events were nontraumatic. A total of 1,317 patients experienced an intracranial bleeding event. The incidence rate of ischemic stroke over the same period was 13.44 per 1000 person-years.

The authors conclude that several factors place patients at an increased risk of traumatic intracranial bleeding including dementia, anticonvulsant use, depression, anemia, and labile INR and that these identified risk factors could help foster discussions with older patients on the benefits and harms of warfarin therapy.  They end by noting that the “findings should be validated in other data sets, particularly given the underrepresentation of women in our sample.”

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