Prevalence of irritable bowel syndrome (IBS) in first-degree relatives of patients with inflammatory bowel disease (IBD)

Background: Epidemiological studies have shown a greater prevalence of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) among first-degree relatives of patients diagnosed of these diseases. However, it is not known whether relatives of patients with IBD have a greater prevalence of IBS than the general population. Aims: To analyse the prevalence of IBS among first-degree relatives by consanguinity (parents, siblings and offspring) and affinity (spouses) of patients with IBD. Materials and methods: A prevalence study was conducted identifying 490 relatives of 91 patients with IBD. Of these, 404 met inclusion criteria; and 360 (response rate: 89.1%) answered the questionnaires. Subjects were invited to participate in the study through index cases (patients with IBD). The following variables were collected: age, sex, history of digestive diseases, kinship and cohabitation with the index case. The relatives completed a questionnaire to identify those who met Rome I and Rome II criteria for IBS. Results: The overall prevalence of IBS among the first-degree relatives of patients with IBD was 49.4% and 10% according to Rome I and Rome II criteria respectively. IBS prevalence was higher in first-degree blood relatives than in spouses of patients (Rome I: 53.1% vs 29.1%, p=0.001; Rome II: 10.8% vs 5.4%, NS). No differences were found in IBS prevalence depending on whether relatives were living with the index case or not. Conclusion: IBS prevalence in first-degree relatives of patients with IBD is elevated. It is significantly greater in blood relatives, which suggests involvement of genetic and psychological factors rather than environmental factors. (C) 2011 European Crohn's and Colitis Organisation. Published by Elsevier B.V. All rights reserved.