Colon to Rectum
J Crohns Colitis. 2023;17(1):30–6
Risk factors for developing inflammatory bowel disease within and across families with a family history of IBD
Introduction: A family history of inflammatory bowel disease (IBD) is the strongest risk factor for disease. However, some first-degree relatives (FDRs) will develop disease, while others will not.
Methods: Using the nationwide Danish National Patient Register, the authors examined risk factors in families with 2 or more affected FDRs. First, they compared exposures between siblings with and without IBD within the same family (within-family analysis). Second, they compared exposures between individuals with and without IBD across all families (across-family analysis). Exposures included sex, birth order, mode of delivery, antibiotics, personal and family history of immune-mediated diseases, gastrointestinal infections, and surgical history preceding diagnosis. Uni- and multivariable conditional logistic regression analyses were conducted.
Results: In the “within-family analysis”, 1669 families were included (1732 cases, 2447 controls). Female sex (adjusted odds ratio [aOR] = 1.40, 95% confidence interval [CI]: 1.23–1.59), history of ankylosing spondylitis (aOR = 2.88, 95% CI: 1.05–7.91) and exposure to antibiotics (aOR = 1.28, 95% CI: 1.02–1.61) increased the risk for IBD. In the “across-family analysis”, 1254 cases and 37,584 controls were included, confirming an association with prior ankylosing spondylitis (aOR = 3.92, 95% CI: 1.38–11.12) and exposure to antibiotics (aOR = 1.29, 95% CI: 1.04–1.60). Having 2 or more relatives (aOR = 6.26, 95% CI: 1.34–29.29) or a sibling with IBD (aOR = 1.36, 95% CI: 1.18–1.57) increased the risk of IBD. Appendectomy reduced the risk of ulcerative colitis (aOR = 0.32, 95% CI: 0.14–0.72).
Conclusion: In families with inflammatory bowel disease (IBD), the authors identified risk factors for the unaffected first-degree relatives to develop disease. These findings provide an opportunity for counselling IBD relatives.