BACKGROUND & AIMS: In this nationwide cohort from Israel (Epi-IIRN), we aimed to characterize risks for age-related complications, mortality and IBD-related surgeries in patients with elderly-onset inflammatory bowel diseases (EO-IBD). METHODS: Data of patients with EO-IBD (≥65 years) diagnosed during 2005-2020 were retrieved from the epi-IIRN database. EO-IBD Patients were compared to 3 age-, sex- and district-matched non-IBD individuals, for age-related outcomes. Incident EO-IBD patients were matched to 4 adult-onset (AO) IBD (≥18<
65 years) by IBD-subtype-, sex- and district. Cumulative incidence functions were calculated to estimate event probabilities over time accounting for death as a competing risk. Proportional subdistribution hazards models were used to assess predictors of medication use, surgery and complications. RESULTS: Of 2,826 EO-IBD cases, 2,162 had 3 matched non-IBD controls. Mortality rates/1000 PY were similar in EO-IBD and non-IBD controls (292.32 (273.53-311.85) vs.291.24 (280.31-302.42), respectively) as were mortality causes and risk (aHR, 95% CI) for pneumonia 1.04 (0.84-1.29), fractures 1.03 (0.82-1.29), bacteremia 2.16 (0.87-5.40) and thromboembolism 0.58 (0.27-1.23). When matching 2,826 EO-IBD to 11,304 AO-IBD, EO-IBD had lower exposure to thiopurines (aHR= 0.44 [0.39-0.49], and anti-TNF (aHR=0.37 [0.32-0.42] and higher risk for abdominal surgery (aHR=1.23 [1.04-1.46] in CD, aHR=1.51 [2.04-3.08] in UC, respectively) but lower perianal surgery risk (HR=0.27 [0.16-0.47]) in CD. The calculated frequencies of repeat perianal and abdominal surgery in EO-CD and AO-CD at 3 years were 7.1% vs. 36%, respectively and 29% and 21%, respectively. CONCLUSIONS: Compared with non-IBD elderly, EO-IBD have similar risk for death and complications. Compared to AO-IBD, EO-IBD are at higher risk for abdominal surgery, but not for perianal surgery.