Adult-onset inflammatory bowel disease and the risk of venous thromboembolism – a Swedish nationwide cohort study 2007–2021

Earlier studies, mainly prior to the widespread use of advanced therapy and implementation of guidelines for thromboprophylaxis indicate a doubled risk of venous thromboembolism (VTE) in patients with inflammatory bowel disease (IBD). Using Swedish healthcare registers, we identified a population-based cohort of patients with incident IBD 2007–2021. Patients were matched by age, sex, calendar year of birth and place of residence with up to 10 reference individuals. The primary outcome was VTE, i.e., pulmonary embolism (PE) and deep vein thrombosis (DVT). Incidence rates (IRs) per 1000 person-years, cumulative incidence and hazard ratios (HRs) were calculated for IBD overall and according to clinical characteristics. The temporal trend of the incidence of VTE by calendar year was presented. We followed 55,252 IBD patients and 536,067 reference individuals, for a median of 6.5 years. The incidence of VTE in IBD was 5.03 <i>vs</i>. 2.35 per 1000 person-years among reference individuals, corresponding to a doubled risk of VTE (HR = 2.12; 95% confidence interval [CI] 2.02–2.23). Particularly high risks were seen in the first year of follow-up, and among patients with extensive ulcerative colitis (UC), primary sclerosing cholangitis (PSC), extraintestinal manifestations, perianal disease and hospitalization at diagnosis. The occurrence of VTE in IBD did not decrease across calendar years. IBD remains linked to an elevated risk of VTE, particularly with disease characteristics associated with a higher inflammatory burden and higher age. Our findings underscore the importance of continuous vigilance and individual assessment of VTE risk in patients with IBD.