Objective: Given the paucity of population-based data on the association between inflammatory bowel diseases [IBD], coeliac disease [CeD], and coeliac autoimmunity [CeA] we aimed to study the associations in a nationwide study.

Methods: Using health administrative data for all four health maintenance organisations in Israel, covering 98% of the population, we explored the prevalence of CeD in children and adults with IBD versus non-IBD matched controls. CeD was defined by three ICD-9 codes and CeA by positivity for tissue transglutaminase antibodies.

Results: In total, 34 375 IBD patients (56% Crohn's disease [CD] and 44% ulcerative colitis [UC]) were compared with 93 603 non-IBD controls. Among IBD patients, 319 [0.93%] had CeD versus 294 [0.31%] non-IBD controls (odds ratio [OR] = 2.97, 95% confidence interval [CI] 2.54-3.48; p <0.001). CeA was identified in 575 [1.67%] IBD patients vs 158 [0.17%] controls [OR = 10.06, 95% CI 8.43-12; p <0.001]. The prevalence of CeD was higher in paediatric-onset IBD (87/5243 [1.66%]) than adult-onset IBD (232/29 132 [0.79%]; p <0.001). CD patients had a higher prevalence of CeD (229/19 264 [1.19%]) than UC patients (90/15 111 [0.56%]; OR = 2.01, 95% CI 1.57-2.56; p <0.001). The diagnosis of CeD preceded the diagnosis of IBD in 241/319 cases [76%]. The time to treatment escalation was shorter in patients with both IBD and CeD than in patients with IBD without CeD [p = 0.017].

Conclusions: CeD and CeA are more prevalent in IBD patients, especially in paediatric-onset IBD and in CD. The diagnosis of CeD usually precedes that of IBD. Having CeD is associated with more intensified treatment for IBD.