[Systematic review and meta-analysis of the prevalence of small intestinal bacterial overgrowth in patients with functional gastrointestinal disorders].

Objective: To systematically evaluate the prevalence of small intestinal bacterial overgrowth (SIBO) in patients with functional gastrointestinal disorders (FGID). Methods: The literature were systematically searched from PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang Data, and VIP Chinese Periodical Database, with the search period from the database establishment to November 20th, 2025. Studies that diagnosed SIBO via breath tests or jejunal/duodenal aspirate culture and FGID based on Rome criteria were included. The trial group consisted of patients with FGID, while the control group comprised individuals without significant gastrointestinal symptoms. According to the inclusion and exclusion criteria, two investigators independently performed literature screening, data extraction, and quality assessment. The outcome measure was the prevalence of SIBO (including the total sample size and the number of positive cases). Data processing and meta-analyses were performed using R software (version 4.5.2). The effect measures were the SIBO prevalence and odds ratio (OR), and heterogeneity was evaluated using the I² statistic. Subgroup analysis (by FGID subtype, testing method, etc.) and regression analysis (variables include age, region, etc.) were conducted. Results: A total of 81 studies were included, involving 6 017 cases in the trial group and 1 826 cases in the control group. The prevalence of SIBO in the trial group was 39.0% (95%CI: 33.3%-44.8%, I2=95.0%), higher than 11.5% (95%CI: 8.7%-14.6%, I2=72.2%) in the control group. FGID patients had an increased risk of SIBO (OR=5.27, 95%CI: 3.91-7.10, P<0.001, I2=58.3%). Subgroup analysis by FGID subtypes showed that the overall prevalence of SIBO in irritable bowel syndrome (IBS) was 40.4% (95%CI: 36.2%-44.9%, I²=93.0%), with the highest prevalence in diarrhea-predominant IBS(IBS-D) (41.3%, 95%CI: 36.6%-46.1%, I2=76.6%); The prevalence of SIBO was 37.9% (95%CI: 26.8%-50.4%, I2=79.5%) in functional constipation (FC) and 30.1% (95%CI: 21.8%-39.9%, I2=84.4%) in functional dyspepsia (FD). Subgroup analysis by testing method showed that lactulose breath test yielded higher prevalence (45.7%, 95%CI: 41.3%-50.2%, I2=91.7%) than glucose breath test (28.7%, 95%CI: 23.6%-34.4%, I2=86.1%) (P<0.001). Regression analysis suggested a weak positive correlation between age and SIBO prevalence (β=0.003, 95%CI: -0.001-0.008, P=0.178), and a higher risk of SIBO in Asian populations compared with non-Asian populations (β=0.182, 95%CI: 0.094-0.278, P<0.001). Conclusions: SIBO prevalence is elevated in patients with FGID, particularly among those with IBS-D;with diagnostic modality and geographic region contributing to variability in estimates.