Antithrombotic drugs and risk of hemorrhagic stroke in the general population

Objective: To investigate the relationship between hemorrhagic stroke and use of antiplatelets and warfarin using data from The Health Improvement Network. Methods: A total of 1,797 incident cases of intracerebral hemorrhage (ICH) and 1,340 of subarachnoid hemorrhage (SAH) were ascertained. Density-based sampling was used to select 10,000 controls free from hemorrhagic stroke. Risk of hemorrhagic stroke was evaluated in current users and nonusers of antiplatelets and warfarin. Unconditional logistic regression models were used to adjust for age, sex, calendar year, alcohol, body mass index, hypertension, and health services utilization. Results: Aspirin use was not associated with an increased risk of ICH (odds ratio [OR] 1.06, 95% confidence interval [CI] 0.93-1.21), but was associated with a decreased risk of SAH (OR 0.82, 95% CI 0.67-1.00), compared with no therapy. Aspirin use >= 3 years was associated with a decreased risk of SAH (OR 0.63, 95% CI 0.45-0.90) compared with no therapy. Warfarin use was associated with a greatly increased risk of ICH (OR 2.82, 95% CI 2.26-3.53) and a moderately increased risk of SAH (OR 1.67, 95% CI 1.15-2.43) compared with no therapy. International normalized ratio values >= 3 carried a marked risk of ICH (OR 7.01, 95% CI 4.10-11.99). Conclusion: Aspirin is not associated with a risk of ICH compared with no therapy. Chronic low-dose aspirin treatment may have a protective effect on the risk of SAH. Warfarin users in this study cohort were at a much higher risk of ICH than those receiving no therapy, with a marked association with international normalized ratio >3.