Epidemiology of Functional Diarrhea and Comparison with Diarrhea-Predominant Irritable Bowel Syndrome: A Population-Based Survey in China

BACKGROUND The epidemiology of functional diarrhea and its impacts on Chinese remain unclear, and there are no data on the comparative epidemiology of functional diarrhea and diarrhea-predominant irritable bowel syndrome (IBS-D). This study was to explore the epidemiology of functional diarrhea and its impacts, and to identify its distinction from IBS-D. METHODS AND FINDINGS A cross-sectional survey was conducted in 16078 respondents, who were interviewed under a randomized stratified multi-stage sampling design in five cities of China. All respondents completed the modified Rome II questionnaire, and the 36-item Short Form health survey (SF-36) was used for assessing health-related quality of life in 20% of the sample. Overall, 248 respondents (1.54%) had functional diarrhea and 277 (1.72%) had IBS-D. Functional diarrhea was positively associated with increasing age and body mass index (trend test P<0.05). The three most common symptoms for at least 3 weeks in the past months were loose, mushy or watery stools (n = 203, 81.85%), more than three bowel movements a day (n = 100, 40.32%) and having to rush to the toilet to have a bowel movement (n = 72, 29.03%). Meaningful impairment was observed in 5 of the 8 SF-36 domains in respondents with functional diarrhea. The demographics are mostly similar between the respondents with functional diarrhea and IBS-D; however, respondents with IBS-D had more frequent symptoms of diarrhea and even lower scores in SF-36 domains than those with functional diarrhea. CONCLUSIONS The prevalence of functional diarrhea in China is substantially lower than that in Western countries and relatively higher than that in other Asian countries. It impaired health-related quality of life, and respondents with IBS-D have even worse quality of life. Further population-based studies are needed to investigate the epidemiology of functional diarrhea and the differences between functional diarrhea and IBS-D.