After first episodes of venous thromboembolism (VTE), patients are at increased risk of recurrent VTE and arterial thrombotic events (ATE) compared with the general population, two disorders that are influenced by anticoagulation. However, risk factors of these conditions occurring during and after anticoagulation are little described. Using cause-specific hazard regression models, we aimed to determine risk factors of the composite outcome recurrent VTE/ATE, and separately recurrent VTE or ATE, during and after anticoagulation in patients with first episodes of VTE from a prospective cohort. Hazard ratios (HRs) are given with 95% confidence intervals (CIs). A total of 2,011 patients treated for at least 3 months were included. A total of 647 patients had recurrent VTE/ATE (incidence: 4.69% per patient-years) during overall follow-up (median: 92 months). Of these events, 173 occurred during anticoagulation (incidence: 3.67% per patient-years). Among patients free of events at the end of anticoagulation, 801 had a post-anticoagulation follow-up ≥3 months; and 95 had recurrent VTE/ATE (incidence: 1.27% per patient-years). After adjustment for confounders, cancer-associated VTE (HR: 2.64, 95% CI: 1.70-4.11) and unprovoked VTE (HR: 1.95, 95% CI: 1.35-2.81) were the identified risk factors of recurrent VTE/ATE during anticoagulation (vs. transient risk factor-related VTE). Risk factors of recurrent VTE/ATE after anticoagulation included 50 to 65 years of age (vs. < 50, HR: 1.99, 95% CI: 1.04-3.81), older than 65 years (vs. < 50, HR: 5.28, 95% CI: 3.03-9.21), and unprovoked VTE (vs. transient risk factor-related VTE, HR: 2.06, 95% CI: 1.27-3.34). Cancer-associated VTE and unprovoked VTE are the main risk factors of recurrent VTE/ATE during anticoagulation, while older age and unprovoked VTE mainly predict the risk of these events after anticoagulation.
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