Sex differences in irritable bowel syndrome in Japanese university students

Background. Epidemiological studies of irritable bowel syndrome (IBS) among young adults are few, especially in Asian countries. Our aim was to examine the prevalence of IBS, whether there was a sex difference, and whether allergic diseases were important risk factors for IBS in young adults. Methods. Newly enrolled university students completed health survey questionnaires regarding general health. Those with gastrointestinal symptoms completed the Gastrointestinal Symptom Rating Scale (GSRS) and an additional questionnaire covering the presence of allergic manifestations. IBS was diagnosed based on the Rome II criteria. Results. IBS was diagnosed in 268 of 2495 students [10.7%; constipation-predominant type (IBS-C), 128; diarrhea-predominant type (IBS-D), 117; unclassified, 23]. IBS-C was associated with female sex (odds ratio, 6.4; 95% confidence interval, 4.1-9.7; P < 0.001), whereas there was no sex difference in IBS-D. The proportions of subjects with food sensitivity were significantly different among the three groups (4.0%, subjects without IBS; 8.6%, IBS-C group; and 15.4%, IBS-D group) (P < 0.001). The median GSRS scores for pain (1.67 vs 1, P = 0.001), indigestion (1.75 vs 1.5, P < 0.001), and constipation (2.0 vs 1.33, P < 0.001) were higher, and the median diarrhea score was lower (1.33 vs 1.67) (P < 0.001), in women than in men. The median score for diarrhea (2.33 vs 1.67, P = 0.001) was significantly higher in subjects with food sensitivity than in those without. Conclusions. There was a strong relationship between IBS-C and female sex, and food sensitivity seemed to be an exacerbating factor for IBS-D.