High Prevalence of Irritable Bowel Syndrome in Medical Outpatients in Japan

Background and Goals: The prevalence of irritable bowel syndrome (IBS) among Japanese patients who visit hospitals departments of internal medicine is thought to be high. However, no clear statistical evidence has been provided to support such a claim. We tested the hypotheses that the prevalence of IBS in medical outpatients clinics in Japan is high, and that IBS patients feel more psychosocial stress than patients without IBS. Study: The subjects in this study were 633 patients who visited participating physicians. Patients were asked to fill in the Japanese version of the Rome II Modular Questionnaire (RIIMQ) for IBS diagnosis, the Self-reported Irritable Bowel Syndrome Questionnaire (SIBSQ) for severity of the disease and the demographic questionnaire for perceived stress and life style. Results: Rome II-defined IBS was diagnosed in 196 patients (31%). Analysis of variance revealed significant difference in the IBS scores of SIBSQ among IBS subjects (39.0 ± 11.1, mean ± SD), functional bowel disorder subjects (27.1 ± 10.2), and normal subjects (24.0 ± 10.0, P < 0.01). The prevalence of IBS depending on age formed 2 peaks, one among adolescents and the other among the elderly. IBS patients had significantly more perceived stress (P < 0.0001), irregular sleep habit (P < 0.0001), and irregular meal habit (P < 0.0001) than those without IBS. Conclusions: The prevalence of IBS among medical outpatients in Japan is high (31%). IBS subjects among medically ill patients are thought to have more perceived stress and less regular life styles.