Reduced risk of death with warfarin - results of an observational nationwide study of 20 442 patients with atrial fibrillation and ischaemic stroke

Abstract

Background: Warfarin is demonstrated to be superior in efficacy over antiplatelet agents for the prevention of stroke, but the relationship between warfarin and mortality is less clear. Our aim was to investigate this relationship in a large cohort of unselected patients with atrial fibrillation and ischaemic stroke.

Methods: This observational study was based on patients who were discharged alive and registered in the Swedish Stroke Register in 2001 through 2005. Vital status was retrieved by linkage to the Swedish Cause of Death Register. We calculated a propensity score for the likelihood of warfarin prescription at discharge from hospital. The risk of death and 95% confidence intervals were estimated in Cox regression models.

Results: Out of the 20 442 patients with atrial fibrillation and ischaemic stroke (mean age = 79·5 years), 31% (n = 6399) were prescribed warfarin. After adjustment for the propensity score, warfarin was associated with a reduced risk of death (0·67; 95% confidence interval, 0·63-0·71). The crude rate (per 100 person-years) of fatal non-haemorrhagic stroke was lower in patients who received warfarin (1·60; 95% confidence interval, 1·34-1·89) compared to those who received antiplatelet (6·83; 95% confidence interval, 6·42-7·25). The rates (per 100 person-years) of fatal haemorrhagic stroke were 0·21 (95% confidence interval, 0·12-0·32) and 0·43 (95% confidence interval, 0·34-0·55) in patients prescribed warfarin and antiplatelet therapy, respectively.

Conclusions: In addition to its established benefit for stroke prevention, warfarin therapy in patients with atrial fibrillation and ischaemic stroke was associated with a reduced risk of death, without an increased risk of fatal haemorrhagic stroke.

Keywords: anticoagulants; antiplatelets; atrial fibrillation; epidemiology; ischaemic stroke; mortality.