Risk of ulcerative colitis and Crohn's disease among offspring of patientswith chronic inflammatory bowel disease

OBJECTIVE: The incidence of inflammatory bowel disease (IBD) varies among a nd within countries, but several studies have indicated that genetic factor s may play an important role in the etiology of IBD. A Danish regional stud y has observed an almost 10-fold increased risk for ulcerative colitis (UC) and Crohn's disease (CD) among first-degree relatives of patients with the se diseases. To give more precise risk estimates we conducted a nationwide study using population-based data from the Danish National Registry of Pati ents (NRP). METHODS: All patients from the entire Danish population (5.2 million), who were discharged between 1977 and 1992 with a diagnosis of either UC or CD w ere extracted from the NRP. The offspring of these patients born in 1958 or later were identified in the Civil Registration System and subsequently li nked to the NRP by means of the civil registration number. All Danish citiz ens alive or born on April 1, 1968 or later no registered in the Civil Regi stration System by a unique registration number, which includes the data of birth and links the offspring to their parents. The prevalence proportion ratio (PPR) was estimated by dividing the observed number of offspring with UC or CD, respectively, with the expected number of cases from the general population. RESULTS: The PPRs of CD and UC among offspring of patients with UC were 2.6 and 5.1, respectively, and the PPRs of CD and UC among offspring of patien ts with CD were 12.8 and 4.0, respectively. All ratios were significantly i ncreased. CONCLUSION: The risk for UC and CD among offspring of patients with IBD is 2-13 times higher than the risk within the general population. (C) 1999 by Am. Cell. of Gastroenterology.