DOP63 Mortality in Pediatric-onset Immune-Mediated Inflammatory Disease – A Nationwide Study

Background Patients with pediatric-onset immune-mediated inflammatory diseases (pIMID) show more aggressive phenotypes compared to patients diagnosed as adults. Despite this, data on mortality is extrapolated from patients diagnosed in adulthood, which might underestimate the actual risk. We aim to estimate the effect of pIMID compared to reference individuals from the general population on the long-term risk of all-cause mortality. Methods A population-based cohort study using the nationwide Danish health care registers. We included all patients diagnosed with pIMID in Denmark from 1980 to 2018 and matched them to up to ten reference individuals from the general population (with no recorded IMID) based on sex, age at diagnosis, and area of residence. Exposure was pIMID, defined as ICD codes indicative of autoimmune hepatitis, primary sclerosing cholangitis, Crohn’s disease, ulcerative colitis, juvenile idiopathic arthritis, system lupus erythematosus, or vasculitis registered before age 18. The primary outcome was all-cause mortality. The secondary outcome was cause-specific mortality. Cox survival analysis was used to estimate hazard ratios (HR) and Aalen survival analysis to estimate rate differences with corresponding 95% confidence intervals (CI) adjusted for the year of diagnosis and family income. Denmark has universal free health care, and health care data can be accessed through the nationwide health registers, continuously updated since 1980. Results We included 11,581 individuals diagnosed with pIMID, and 99,665 matched reference individuals, accounting for 1,371,994 person-years of follow-up. Median age at pIMID diagnosis was 12.6 years (IQR: 7.9 – 15.9). During follow-up, 152 pIMID patients and 316 reference individuals died, resulting in an all-cause mortality adjusted HR (aHR) of 3.8 (95% confidence interval [CI]: 3.1-4.7) compared to reference individuals without pIMID. This corresponded to 7.8 (95%CI: 6.1-9.5) additional deaths per 10,000 person-years. The strongest associations were found for gastrointestinal disorders (aHR 22.8 [95%CI: 9.6-64.1]), gastrointestinal cancers (aHR 19.2 [95%CI: 5.0-74.2]), and lymphoproliferative diseases (aHR 6.8 [95%CI: 2.8-16.8]). The aHR of suicide was 2.9 (95%CI: 1.6-5.0). Conclusion Patients diagnosed with pIMID have a four-fold increased risk of mortality when followed into adulthood. This underlines the severe disease course of pIMID and highlights the need for lifelong multidisciplinary care.