Demographic details and surgical histories of patients approached
| Ulcerative colitis | Crohn’s disease | Controls | |
| No of subjects | 213 (100) | 110 (100) | 337 (100) |
| Men | 99 (46) | 41 (37) | 147 (44) |
| Age (y) | |||
| 15–24 | 17 (8) | 12 (11) | 32 (9) |
| 25–34 | 32 (15) | 27 (25) | 61 (18) |
| 35–44 | 44 (21) | 19 (17) | 68 (20) |
| 45–54 | 39 (18) | 21 (19) | 63 (19) |
| 55–64 | 35 (16) | 18 (16) | 56 (17) |
| 65+ | 46 (22) | 13 (12) | 57 (17) |
| Mean (SD) age at diagnosis | 38 (18) | 32 (16) | — |
| Numbers reporting having had1-150: | |||
| Appendicectomy | 9/201 (4.5) | 24/102 (24) | 57/295 (19) |
| Tonsillectomy | 48/197 (24) | 33/100 (33) | 85/298 (29) |
| Cholecystectomy | 5/203 (2.5) | 8/99 (8) | 13/295 (4.4) |
| Hysterectomy | 12/110 (11) | 8/64 (13) | 62/172 (36) |
| Vasectomy | 15/94 (16) | 6/38 (16) | 20/128 (16) |
Results are expressed as number (%) except where otherwise specified.
↵1-150 For whom the question was applicable and excluding those unsure or not responding.