Estimates of familial risk of inflammatory bowel diseases (IBDs), Crohn’s disease (CD), and ulcerative colitis (UC) are needed for counseling of patients and could be used to target future prevention. We aimed to provide comprehensive population-based estimates of familial risk of IBD.
The study encompassed the entire Danish population during 1977–2011 (N=8,295,773; 200 million person-years). From national registries, we obtained information on diagnosis date of IBD (N=45,780) and family ties. Using Poisson regression, we estimated incidence rate ratios (IRRs) of IBD in relatives of IBD cases compared with individuals with relatives of the same type without IBD.
The risk of CD was significantly increased in first-degree (IRR, 7.77; 95% confidence interval (CI), 7.05–8.56), second-degree (IRR, 2.44; 95% CI, 2.01–2.96), and third-degree relatives (IRR, 1.88; 95% CI, 1.30–2.71) to patients with CD, and was less pronounced in relatives to UC cases. Likewise, the risk of UC was increased in first-degree (IRR, 4.08; 95% CI, 3.81–4.38), second-degree (IRR, 1.85; 95% CI, 1.60–2.13), and third-degree relatives (IRR, 1.51; 95% CI, 1.07–2.12) of UC cases, and less pronounced in relatives of CD cases. IRRs increased with two or more IBD-affected relatives and were modified by age, with the highest family-related IRR observed in early life.
The risk of IBD is significantly increased in first -, second-, and third-degree relatives of IBD-affected cases, with up to 12% of all IBD cases being family cases. The risk is particularly pronounced in young individuals.
1Organ Center, Hospital of Southern Jutland, Aabenraa, Denmark
2Institute of Regional Health Research-Center Sønderjylland, University of Southern Denmark, Odense, Denmark
3Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark
4Department of Clinical Epidemiology, University of Aalborg, Aalborg, Denmark
Correspondence: Frederik Trier Moller, MD, Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark. E-mail: firstname.lastname@example.org
Guarantor of the article: Tine Jess, MD, DMSc.
Specific author contributions: Conception and design of the study, generation, analysis and interpretation of data, drafting the manuscript and approval of the final version of the manuscript: FTM; interpretation of data and revision and approval of the final version of the manuscript: VA; design of the study, analysis and interpretation of data, revision and approval of the final version of the manuscript: JW; conception and design of the study, generation and interpretation of data, drafting and critical revision of the manuscript and approval of the final version of the manuscript: TJ.
Financial support: This study was supported by Region of Southern Denmark, University of Southern Denmark, Hospital of Southern Jutland and Beckett foundation.
Potential competing interests: Vibeke Andersen is an adviser and member of advisory board for MSD/Merck and Jansen.
SUPPLEMENTARY MATERIAL accompanies this paper at http://links.lww.com/AJG/B64