Background: Recommendations for venous thromboembolism (VTE) prophylaxis in patients with inflammatory bowel disease (IBD) can be refined by incorporating patient-specific risk factors. Objectives: To determine the risk of deep venous thrombosis (DVT) and pulmonary embolism (PE) in children and adults with Crohn's disease and ulcerative colitis and evaluate whether this risk varies by age and/or presence of other risk factors. Methods: We performed a cohort study using Danish administrative data. Incidence rates of DVT and PE were calculated among patients with IBD and an age- and gender-matched comparison population and compared using Cox proportional hazards regression. We performed additional analyses stratifying by age, gender and disease type and restricting outcomes to unprovoked events (occurring without known malignancy, surgery, fracture/trauma or pregnancy). We next performed a nested case-control study to adjust for additional co-morbidities (congestive heart failure, diabetes, myocardial infarction and stroke) and the use of hormone replacement and antipsychotic medications. Results: The study included 49 799 patients with IBD (14 211 Crohn's disease, 35 229 ulcerative colitis) and 477 504 members of the general population. VTE risk was elevated in patients with IBD (HR=2.0 (95% CI 1.8 to 2.1) for total events, HR=1.6 (95% CI 1.5 to 1.8) for unprovoked events). Although the incidence of VTE increased with age, the RR was higher in younger patients. Among those ≤20 years old, HRs were 6.0 (95% CI 2.5 to 14.7) for DVT and 6.4 (95% CI 2.0 to 20.3) for PE. After further adjusting for co-morbidity and medication use in the case-control analysis, ORs for all events remained in the 1.5-1.8 range. Discussion: Patients with IBD have twice the incidence of PE or DVT as does the general population. This risk persisted after taking into account other VTE risk factors. Relative risks were particularly high at young ages, though actual incidence increased with age. These findings can further inform risk-benefit analysis of VTE prophylaxis.
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