Demographic characteristics of the CD study population based on the Montreal classification [27].

For each variable, the number of patients included is given.1Disease behaviour was defined according to the Montreal classification [27]. The stricturing disease phenotype was defined as the presence of stenoses without penetrating disease. The diagnosis of stenoses was made surgically, endoscopically, or radiologically (using MR enteroclysis).2The clinical course of CD was furthermore defined as “aggressive” in CD patients with a stricturing and/or penetrating disease behaviour and/or when CD-related surgery became necessary.3Immunosuppressive agents included azathioprine, 6-mercaptopurine, methotrexate, infliximab, and/or adalimumab.4Only surgery related to CD-specific problems (e.g., ileocecal resection, fistulectomy, colectomy, and ileostomy) was included.Demographic characteristics of the CD study population based on the Montreal classification [27].