Table 1.
General characteristics of patients with IBD in Norway and Sweden, 1987–2016
| Characteristics | Norway, 1987–2015 | Sweden, 1993–2016 | Total |
| Total, n | 44 452 | 87 040 | 131 492 |
| Total person-years | 483 293 | 839 539 | 1 322 831 |
| Median follow-up years (IQR) | 9.9 (4.2–16.7) | 9.3 (4.3–14.5) | 9.6 (4.3–14.9) |
| Sex (n, %) | |||
| Female | 21 709 (48.8) | 42 182 (48.5) | 63 891 (48.5) |
| Male | 22 743 (51.1) | 44 858 (51.5) | 67 601 (51.4) |
| Age (years) at IBD diagnosis (n, %) | |||
| <20 | 5119 (11.5) | 9516 (10.9) | 14 635 (11.1) |
| 20–39 | 17 523 (39.4) | 30 680 (35.2) | 48 203 (36.6) |
| 40–59 | 13 514 (30.4) | 28 212 (32.4) | 41 726 (31.7) |
| 60+ | 8296 (18.6) | 18 632 (21.4) | 26 928 (20.4) |
| Calendar year at IBD diagnosis* (n, %) | |||
| 1987/1993–2002 | 20 649 (46.4) | 39 114 (44.9) | 59 763 (45.4) |
| 2003–2015/2016 | 23 803 (53.5) | 47 926 (55.1) | 71 729 (54.5) |
| IBD subtype (n %) | |||
| Ulcerative colitis | 27 214 (61.2) | 51 130 (58.7) | 78 344 (59.5) |
| Crohn’s disease | 13 347 (30.0) | 28 900 (33.2) | 42 247 (32.1) |
| IBD unclassified | 3891 (8.7) | 7010 (8.1) | 10 901 (8.2) |
| Extent of ulcerative colitis† (n, %) | |||
| E1 (proctitis) | 6007 (22.1) | 6326 (12.4) | 12 333 (15.7) |
| E2 (left-sided) | 2380 (8.7) | 10 836 (21.2) | 13 216 (16.8) |
| E3 (extensive) | 14 621 (53.7) | 24 649 (48.2) | 39 270 (50.1) |
| Ex (not defined) | 4206 (15.4) | 9319 (18.2) | 13 525 (17.2) |
| Location of Crohn’s disease† (n, %) | |||
| L1 (terminal ileitis) | 3126 (23.4) | 5768 (20.0) | 8894 (21) |
| L2 (colonic) | 2970 (22.2) | 5666 (19.6) | 8636 (20.4) |
| L3 (ileocecal) | 5453 (40.8) | 12 879 (44.6) | 18 332 (43.3) |
| Lx (not defined) | 1798 (13.4) | 4587 (15.9) | 6385 (15.1) |
| Behaviour of Crohn’s disease† (n, %) | |||
| B1 (non-stricturing/non-penetrating) | 10 392 (77.8) | 21 789 (75.4) | 32 181 (76.1) |
| B2 (stricturing) | 1620 (12.1) | 5138 (17.8) | 6758 (15.9) |
| B3 (penetrating) | 931 (6.9) | 1092 (3.8) | 2023 (4.7) |
| B2B3 (stricturing and penetrating) | 404 (3.0) | 881 (3.0) | 1285 (3.0) |
| Perianal disease of Crohn’s disease† (n, %) | |||
| 1991 (14.9) | 5928 (20.5) | 7919 (18.7) | |
| Primary sclerosing cholangitis (n, %) | |||
| 1035 (2.3) | 3111 (3.6) | 4146 (3.1) | |
| Bowel surgery during follow-up‡ (n, %) | |||
| 8828 (19.8) | 10 392 (11.9) | 19 220 (14.6) |
*Patients diagnosed before 2002 could represent a mix of prevalent and incident patients with IBD as outpatient data were gradually included in the Norwegian hospital databases and the Swedish National Patient Register.
†Definitions and diagnostic codes were used according to the Montreal classifications using ICD-9 and ICD-10 in Norwegian data and ICD-10 in Swedish data representing maximum disease involvement during follow-up. See online supplemental table 2 for definitions.
‡Bowel surgeries included colectomy, small bowel resection, rectal resection, and colon resection during follow-up. See online supplemental table 3 for definitions.
IBD, inflammatory bowel disease; ICD, International Classification of Disease.