Incidence and Predictors of Hemorrhagic Stroke in Users of Low-Dose Acetylsalicylic Acid

Background: The use of antithrombotic drugs (anticoagulants and antiplatelet drugs) has been reported to increase the risk of hemorrhagic stroke (HS) relative to no treatment. This study was performed to characterize the incidence and predictors of HS in users of acetylsalicylic acid (ASA) for the secondary prevention of cardiovascular events. Methods: A cohort of 36,775 ASA users aged 50-84 years in 2000-2007 was identified from The Health Improvement Network database. The incidence of HS was calculated, and a nested case-control analysis, adjusted for potential confounding factors, was performed to calculate the odds ratios (ORs) and 95% confidence intervals (CIs) for the association of potential risk factors with HS in current users of ASA. Results: The overall incidence of HS was 5.70 cases per 10,000 person-years and increased with age. In current ASA users, the incidence of HS was 4.91 cases per 10,000 person-years. Predictors of HS in patients taking ASA for secondary prevention included a history of HS (OR, 4.84; 95% CI, 1.48-15.88), a history of atrial fibrillation (OR, 4.03; 95% CI, 1.53-10.62), and hypnotic/anxiolytic drug use (OR, 2.67; 95% CI, 1.17-6.05). The small number of patients using warfarin also had an increased risk of HS (OR, 23.42; 95% CI, 4.89-112.10). Conclusions: Physicians should consider additional risk factors for HS, such as a history of HS or atrial fibrillation, and the use of warfarin, before prescribing ASA for the secondary prevention of cardiovascular events.