Warfarin Linked to Increased Risk of Intracranial Bleeding in Elderly Patients

A new study suggests that the use of Warfarin may increase the risk of intracranial bleeding more so than previously thought. 

In order to determine the incidence of and risk factors for traumatic intracranial bleeding in elderly patients who were newly prescribed Warfarin sodium, researchers conducted a recent retrospective cohort study at the US Department of Veterans Affairs (VA).

Participants of the study included 31,951 veterans with atrial fibrillation, 75 years or older, who were new referrals to VA anticoagulation clinics from January 1, 2012 to December 31, 2012. While core analysis dates were March 2014 through May 2015, and subsequent ad hoc analyses were performed through December 2015. Clinical characteristics, laboratory outcomes, and pharmacy information were examined from the VA electronic medical record. For traumatic intracranial bleeding, Cox proportional hazards regression was used so that researchers could properly determine predictors of interest selected a priori based on prior known associations.

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 “We used International Classification of Diseases, Ninth Revision, Clinical Modification codes to identify the incidence rates of these outcomes after Warfarin initiation using VA administrative data (in-system hospitalizations) and Medicare fee-for-service claims data (out-of-system hospitalizations),” researchers said.

Researchers determined that abnormal renal or liver function, antihypertensive use, and fall within the last year, may be independent risk factors for intracranial bleeding in elderly patients with atrial fibrillation initiating Warfarin therapy. The primary outcome was hospitalization for traumatic intracranial bleeding (incidence rate: 4.80 per 1000 person-years). Secondary outcomes included hospitalization for any intracranial bleeding or ischemic stroke.

After modifying for possible confounders, the remaining significant predictors for traumatic intracranial bleeding were anemia (hazard ratio [HR], 1.23; 95% CI, 1.00-1.52), anticonvulsant use (HR, 1.35; 95% CI, 1.04-1.75), dementia (HR 1.76; 95% CI, 1.26-2.46), depression (HR, 1.30; 95% CI, 1.05-1.61), and labile international normalized ratio (HR, 1.33; 95% CI, 1.04-1.72).­—Alessia D’Anna

Reference:  Dodson JA, Petrone A, Gagnon DR, Tinetti ME, Krumholz HM, Gaziano M. Incidence and determinants of traumatic intracranial bleeding among older veterans receiving warfarin for atrial fibrillation. JAMA Cardiol. March 9, 2016.