Objectives: The aim of the study was to assess prevalence, incidence, recovery, and risk factors of irritable bowel syndrome according to different definitions in a large random population.
Design: A 5 year follow-up study of a sex- and age-stratified random sample of 4581 Danes interviewed about abdominal symptoms.
Setting: The Glostrup Populations Studies Unit at Glostrup County Hospital.
Main outcome measures: Prevalence, incidence, recovery, and the association of risk factors to irritable bowel syndrome (IBS). The percentage of subjects common to the populations selected by the various definitions of IBS.
Results: According to various definitions, the prevalence of IBS varied from 5 to 65% and the incidence varied from 1 to 36%. At the 5 year follow-up only 5% of subjects with IBS were completely free of all symptoms. Psychological vulnerability and the experience of having problems were strongly associated with prevalence and incidence of IBS, whereas lifestyle factors only showed a very weak or no relationship to IBS. Populations defined as suffering from IBS according to the various definitions had less than 50% of the subjects in common.
Conclusions: Irritable bowel syndrome is frequent but fluctuating in the general population. Psychological factors seem to be of greater aetiological importance to IBS than lifestyle factors. However, a generally accepted and precise definition is essential to make future studies comparable and to allow general conclusions to be drawn. Furthermore, it still needs to be verified whether the syndrome is a disease entity or just an acceptable, common life-condition.