Use of Coumarin Anticoagulants and Cerebral Microbleeds in the General Population

Background and Purpose It remains undetermined whether the use of coumarin anticoagulants associates with cerebral microbleeds in the general population. We investigated whether (1) coumarin use relates to higher prevalence and incidence of microbleeds, (2) microbleeds are more frequent in people with higher maximum international normalized ratios (INRs), and (3) among coumarin users, variability in INR associates with microbleed presence. Methods From the population-based Rotterdam Study, 4945 participants aged 45 years were included in the cross-sectional analysis, and 3069 participants had follow-up brain MRI. Information on coumarin use was obtained from automated pharmacy records. Coumarin users were monitored, and INR values were measured in consecutive visits. Presence and location of microbleeds were rated on brain MRI. We investigated the association of coumarin use with microbleeds using multivariable logistic regression. Results Overall, 8.6% had used coumarin anticoagulants before the first MRI and 5.9% before follow-up MRI. The prevalence of microbleeds was 19.4%, and the incidence was 6.9% during a mean follow-up of 3.9 years (SD, 0.5). Compared with never users, coumarin users had a higher prevalence of deep or infratentorial microbleeds and a higher incidence of any microbleeds, although statistical significance was not reached in the latter. A higher maximum INR was associated with deep or infratentorial microbleeds. Among coumarin users, a greater variability in INR was associated with a higher prevalence of microbleeds. Conclusions Coumarin use is associated with microbleeds. Associations were strongest for people with greater variability in INR.