BACKGROUND: Inflammatory bowel disease (IBD) is a chronic inflammatory disorder. Systemic inflammation increases the risk of atherosclerosis and ischaemic heart disease (IHD).

OBJECTIVE: To examine the impact of IBD, including its duration and treatment, on the risk of IHD.

METHODS: In a nationwide population-based cohort of 4.6 million Danes aged ≥ 15 years, we compared people diagnosed with IBD during 1997-2009 (n=28 833) with IBD-free individuals. Subjects with IHD were identified in the National Patient Register. Using Poisson regression, we estimated the incidence rate ratios (IRRs) for IHD with 95% CI with adjustment for age, gender, socioeconomic status, calendar year and use of drugs for comorbidities.

RESULTS: A markedly increased risk of IHD was seen within the first year after IBD diagnosis (IRR=2.13 95% CI 1.91 to 2.38). During 1-13 years of follow-up after IBD diagnosis, the risk of IHD was 1.22 (95% CI 1.14 to 1.30). The risk of IHD was lower among patients with IBD using 5-aminosalicylic acids (IRR=1.16; 95% CI 1.06 to 1.26) than among non-users (IRR=1.36; 95% CI 1.22 to 1.51) (p=0.02), in particular among oral corticosteroid users, used as a proxy for disease severity. Likewise patients treated surgically or with thiopurines and tumour necrosis factor α antagonists tended to have reduced IRRs for IHD.

CONCLUSIONS: The risk of IHD was highest in the first year after IBD diagnosis, possibly owing to ascertainment bias. The increased long-term risk of IHD in IBD may be related to chronic inflammation, and interventions reducing the inflammatory burden may attenuate this risk.