The overall strength of association was directly related to the number of affected first-degree relatives and was modified by IBD subtype and age of diagnosis.
Familial history for inflammatory bowel disease should be considered for disease screening programs, according to new data from a Swedish cohort.
A team, led by Jonas F. Halfvarson, MD, Department of Gastroenterology, Faculty of Medicine and Health, Örebro University, estimated the prevalence of familial aggregation of IBD.
“A family history of IBD is a proxy for an individual’s genetic and, in part, environmental risk of developing the disease and has long been recognized as the strongest risk factor for IBD,” the authors wrote. “Therefore, family history is routinely assessed as part of the clinical work-up at diagnosis.”
In the past, several studies have focused on familial clustering of IBD. However, the majority of these studies are based on smaller patient populations without including control groups.
In the nationwide, case-control study, the investigators compared patients with IBD (n = 50,667) to a control group (n = 506,720) between 2003-2017 and examined the odds of having a first-degree relative with IBD by age of diagnosis, type of family history, and IBD subtype. They also assessed the incidence of future IBD in relatives of patients with incident IBD.
Of the patients with IBD, 14,927 had Crohn’s disease and 27,221 had ulcerative colitis, while 8519 had unclassified IBD.
Each patient with IBD was identified from Swedish national registers.
The team calculated odds ratios as estimates of relative risk for IBD in first-degree relatives using logistic regression. They also estimated incidence rates of an incident diagnosis of IBD in first-degree relatives of patients with IBDand in first-degree relatives of matched reference individuals from the general population as the number of events per 1000 person-years.
The investigators found patients with IBD more often had a mother (3.0% vs 0.9%; OR, 3.5; 95% CI, 3.3–3.7), father (2.9% vs 0.8%; OR, 3.5; 95% CI, 3.3–3.7), full sibling (5.3% vs 1.5%; OR, 3.6; 95% CI, 3.4–3.8), and child (2.4% vs 0.9%; OR, 2.6; 95% CI, 2.4–2.8) with IBD.
The overall strength of association was directly related to the number of affected first-degree relatives. This strength was also modified by subtype of IBD and age of diagnosis.
The highest odds ratios were seen in pediatric patients with IBD among a subset of pediatric patients with Crohn’s disease (OR, 10.6; 95% CI, 8.2–13.5) and pediatric-onset ulcerative colitis (OR, 8.4; 95% CI, 6.4–10.9) cases.
The 10-year cumulative incidence of disease for full-siblings was 1.7% of incident patients with IBD, compared to 0.4% among full-siblings of reference individuals.
“The variations in the strength of familial IBD and future risk of IBD in [first-degree relatives] support differences in genetic predisposition and call for targeted approaches in potential screening programs,” the authors wrote.
The study, “Age determines the risk of familial inflammatory bowel disease—A nationwide study,” was published online in Alimentary Pharmacology & Therapeutics.