Abstract 12926: New Use of Low-dose Aspirin is Not Associated With a Significantly Increased Risk of Intracranial Bleeds: Results From a Population-based Nested Case-control Study in the United Kingdom

Abstract

Introduction: Low-dose aspirin protects against ischemic cardio- and cerebrovascular disease (CVD/CeVD) and colorectal cancer yet may be associated with a small increased risk of intracranial bleeds (ICB). Aim: To quantify the risk of ICB associated with new use of low-dose aspirin for CVD/CeVD prevention using The Health Improvement Network in the UK. Methods: From a source population aged 40-84 years from 2000-2012 and free of previous low-dose aspirin use, a cohort of new users of low-dose aspirin (75-300 mg; N=199,049) was identified. Each member was matched to a person free of low-dose aspirin on that day by age, sex and primary care practitioner visits in the previous year. Cohorts (mean age at entry, 59.6 years) were followed for up to 14 years (median 5.4 years) to identify incident cases of ICB, with validation by manual review of patient records and/or linkage to hospitalization data. Nested case-control analysis was conducted using cases from both cohorts. To account for changes in aspirin exposure over time, an ‘as-treated’ analysis was used. Controls (n=10,000) were frequency-matched to cases by age, sex and calendar year. Two definitions of current use were used for low-dose aspirin: use on i) 0-7 days or ii) 0-365 days before the index date (ICB date for cases, random date for controls). Adjusted odds ratios (ORs) with 95% confidence intervals (CIs) were calculated by logistic regression overall and stratified by CVD/CeVD status at study entry (primary or secondary prevention populations). Results: A total of 1635 incident cases of ICB were identified. As shown in the Table, compared with never use, current use of low-dose aspirin was not associated with a significant increase risk of ICB among the primary or secondary CVD/CeVD prevention populations, or any ICB subtype. For current use, no significant changes in ICB risk were seen between doses of 75mg, 150mg and 300mg. Conclusions: New use of low-dose aspirin does not significantly increase the risk of any type of ICB.