Objective To determine the risk and outcomes of serious bleeding events in patients with atherosclerotic vascular disease or risk factors.

Methods 68 375 outpatients with prior ischaemic vascular events or multiple atherosclerotic risk factors were followed in this prospective observational study; 64 977 had 1-year follow-up data. Main outcome measures were rates of serious bleeding events and 1-year outcomes for patients with and without serious bleeding events.

Results The 1-year rate of serious haemorrhage was 0.92%, with a cerebral haemorrhage rate of 0.11%. Patients with symptomatic vascular disease had a haemorrhage rate of 1.0%, compared with 0.59% in those with risk factors only. Risk factors for serious bleeding included age, smoking, hypertension, diabetes, congestive heart failure, use of antithrombotics and polyvascular disease. Bleeding risk increased with the use of anticoagulants (OR 1.99, 95% CI 1.38 to 2.86, p<0.001) or antiplatelet agents combined with anticoagulants (OR 2.54, 95% CI 1.74 to 3.71, p<0.001). By logistic regression analysis, patients with a serious bleed (excluding cerebral haemorrhage) had a more than threefold increased risk (HR 3.25, 95% CI 2.58 to 4.10, p<0.0001) of a significant vascular outcome (myocardial infarction, stroke, vascular death) compared with patients without a serious bleed.

Conclusions Serious bleeding complications were relatively rare, but significant considering the large population at risk. Predictors of increased bleeding were similar to the risk factors for ischaemic events. Patients who experienced a serious bleed had a significantly higher rate of major vascular events.