Socioeconomic status and risk of hemorrhage during warfarin therapy for atrial fibrillation: a population-based study

Background — Among patients taking warfarin, lower socioeconomic status is associated with poorer control of anticoagulation. However, the extent to which socioeconomic status influences the risk of hemorrhage is unknown. The researchers examined the extent to which socioeconomic status influences the risk of hemorrhage in older individuals newly commencing warfarin therapy for atrial fibrillation.

Methods — The researchers conducted a population-based cohort study of individuals aged 66 years or older with atrial fibrillation who commenced warfarin therapy between April 1st 1997 and November 30th 2011 in Ontario, Canada. The researchers used neighbourhood-level income quintiles as a measure of socioeconomic status. The primary outcome was an emergency department visit or hospitalization for hemorrhage and the secondary outcome was fatal hemorrhage.

Results — The researchers studied 166,742 older patients with atrial fibrillation who commenced warfarin therapy. Of these, 16,371 (9.8%) were hospitalized for hemorrhage during a median follow-up of 369 (interquartile range 102 to 865) days. After multivariable adjustment using Cox proportional hazards regression, the researchers found that those in the lowest income quintile faced an increased risk of hospitalization for hemorrhage relative to those in the highest quintile (adjusted hazard ratio 1.18; 95% confidence interval 1.12 to 1.23). Similarly, the risk of fatal hemorrhage (n=1,802) was increased in the lowest relative to the highest income quintile (adjusted hazard ratio 1.28; 95% confidence interval 1.11 to 1.48).

Conclusions — Among older individuals receiving warfarin therapy for atrial fibrillation, lower socioeconomic status is a risk factor for hemorrhage and hemorrhage-related mortality. This factor should be carefully considered when initiating and monitoring warfarin therapy.