title: Risk of ulcerative colitis and Crohn's disease among offspring of patients with chronic inflammatory bowel disease.
abstract: OBJECTIVE
  The incidence of inflammatory bowel disease (IBD) varies among and within countries, but several studies have indicated that genetic factors may play an important role in the etiology of IBD. A Danish regional study has observed an almost 10-fold increased risk for ulcerative colitis (UC) and Crohn's disease (CD) among first-degree relatives of patients with these diseases. To give more precise risk estimates we conducted a nationwide study using population-based data from the Danish National Registry of Patients (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 were extracted from the NRP. The offspring of these patients born in 1958 or later were identified in the Civil Registration System and subsequently linked to the NRP by means of the civil registration number. All Danish citizens alive or born on April 1, 1968 or later are registered in the Civil Registration 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 patients with CD were 12.8 and 4.0, respectively. All ratios were significantly increased.
  
  
  CONCLUSIONS
  The risk for UC and CD among offspring of patients with IBD is 2-13 times higher than the risk within the general population.
authors.affiliation: Department of Internal Medicine, Elsinore Hospital, Denmark.
authors.forename: M
authors.initials: M
authors.lastname: Orholm
authors.forename: K
authors.initials: K
authors.lastname: Fonager
authors.forename: H T
authors.initials: HT
authors.lastname: Sørensen
mesh_terms: D002648:Child; D002908:Chronic Disease; D003093:Colitis, Ulcerative / Q000235:genetics*; D016001:Confidence Intervals; D003424:Crohn Disease / Q000235:genetics*; D003718:Denmark; D005260:Female; D006801:Humans; D015994:Incidence; D015212:Inflammatory Bowel Diseases / Q000235:genetics*; D008297:Male; D016012:Poisson Distribution; D011159:Population Surveillance; D015995:Prevalence; D012042:Registries; D012307:Risk Factors; D012737:Sex Factors