Table 1 Demographic and clinical features of the studied patients

Total patient-years of follow-up (years)

8875.3

Median (IQR) (years)

11.3 (7.4–16.3)

Demographic features

Age at diagnosis of UC, median (IQR) (years)

41.0 (32–51)

Sex, female, n (%)

343 (46.3)

Family history of IBD, n (%)

68 (9.2)

History of appendectomy

20 (2.7)

Current or ex-smoker

299 (40.4)

Extraintestinal manifestation, n (%)

21 (2.8)

PSC, n (%)

9 (1.2)

Maximum extent of UC

Proctitis (E1), n (%)

197 (26.6)

Left-sided colitis (E2), n (%)

240 (32.4)

Extensive colitis (E3), n (%)

290 (39.1)

Not enough data, n (%)

4 (0.5)

History of immunosuppressive drug use for IBD

CS (prednisolone or methylprednisolone), n (%)

423 (57.1)

IS (azathioprine/6-mercaptopurine, methotrexate, cyclosporine, or tacrolimus), n (%)

191 (25.8)

Biologics (infliximab, adalimumab, golimumab, or vedolizumab), n (%)

79 (10.7)