TABLE 2.
Association of history of inflammatory bowel disease (IBD) in first-degree relatives (FDRs, including parents, full siblings and offspring) with risks of overall colorectal cancer (CRC) and early-onset CRC (diagnosed at age < 50 years)
| IBD types in FDRs | Cases | Controls | Age adjusted odds ratio (95% CI)a | Multivariable adjusted odds ratio (95% CI)b | Multivariable + family historyof CRC adjusted odds ratio (95% CI)c |
|---|---|---|---|---|---|
| Overall CRC | |||||
| n | 69 659 | 343 032 | |||
| No IBD | 68 093 (97.8) | 335 356 (97.8) | 1.00 (Ref ) | 1.00 (Ref ) | 1.00 (Ref ) |
| Any IBD | 1566 (2.2) | 7676 (2.2) | 1.00 (0.95–1.06) | 0.98 (0.92–1.03) | 0.96 (0.91–1.02) |
| IBD types | |||||
| Crohn’s disease | 458 (0.7) | 2361 (0.7) | 0.95 (0.86–1.05) | 0.95 (0.86–1.06) | 0.94 (0.84–1.04) |
| Ulcerative colitis | 958 (1.4) | 4573 (1.3) | 1.03 (0.96–1.10) | 0.99 (0.92–1.07) | 0.97 (0.91–1.05) |
| Unclassified IBD | 166 (0.2) | 877 (0.3) | 0.93 (0.79–1.10) | 0.89 (0.75–1.06) | 0.87 (0.73–1.03) |
| Early-onset CRC | |||||
| n | 7769 (11.2) | 38 767 (11.3) | |||
| No IBD | 7639 (98.3) | 38 196 (98.5) | 1.00 (Ref) | 1.00 (Ref) | 1.00 (Ref) |
| Any IBD | 130 (1.7) | 571 (1.5) | 1.14 (0.94–1.38) | 1.11 (0.90–1.36) | 1.08 (0.88–1.33) |
| IBD types | |||||
| Crohn’s disease | 44 (0.6) | 186 (0.5) | 1.17 (0.84–1.63) | 1.21 (0.85–1.72) | 1.17 (0.82–1.67) |
| Ulcerative colitis | 76 (1.0) | 321 (0.8) | 1.18 (0.92–1.52) | 1.11 (0.85–1.47) | 1.09 (0.83–1.44) |
| Unclassified IBD | 13 (0.2) | 70 (0.2) | 0.97 (0.53–1.76) | 0.91 (0.48–1.70) | 0.88 (0.46–1.67) |
Conditional logistic regression was used to account for matching on age, sex, year of birth and county of residence.
Multivariable model was further adjusted for family size (continuous), income levels (fifths), education (≤9 years, 10–12 years, >12 years, missing), total number of previous clinic visits (fifths), number of previous endoscopies (0, 1, 2, ≥3), Charlson comorbidity index score (continuous) and major comorbidities (all binary, including diabetes, cardiovascular disease, non-colorectal cancer, liver disease, chronic pulmonary disease and connective tissue disease).
Further adjusted for family history of CRC in FDRs (no CRC, CRC diagnosed at age ≥ 50 years or CRC diagnosed at age < 50 years).