ObjectiveTo explore the influencing factors of different types of small intestinal bacterial overgrowth (SIBO).MethodsA total of 539 patients who were hospitalized in the Department of Gastroenterology, the Sixth Medical Center of PLA General Hospital from June 2021 to December 2021 and who underwent methane-hydrogen breath test were retrospectively selected. Based on breath test results, patients were divided into SIBO-negative group (n=300) and SIBO-positive group (n=239). The clinical data were compared between two groups. According to the specific values of breath test results, SIBO-positive patients were further divided into hydrogen-producing bacterial overgrowth (hydrogen-positive, n=103), intestinal methanogen overgrowth (methanogen-positive, n=80), and simultaneous methanogen and hydrogen-producing bacterial overgrowth (double positive, n=56) groups. Multivariate logistic regression analysis was employed to identify influencing factors of different SIBO types. Additionally, SIBO-positive patients were categorized by age into <45 years (n=23), 45-60 years (n=82), 60-75 years (n=124), and ≥75 years (n=10) to compare SIBO positivity rates across age groups.ResultsThe patients in SIBO-positive and double positive groups were older and had a lower body mass index (BMI) than those in SIBO-negative group, with statistically significant differences (P<0.05). Compared with the patients in SIBO-negative group, those in hydrogen-positive group showed a higher proportion of history of coronary heart disease, those in methanogen-positive group were older, and higher proportion of statin use, with statistically significant differences(P<0.05). Multivariate logistic regression analysis revealed that, among different SIBO types, a history of coronary heart disease served as an independent risk factor for hydrogen-producing bacterial overgrowth (OR=2.728, 95%CI 1.271-5.857, P=0.010). For methanogen overgrowth, increasing age was identified as an independent risk factor (OR=1.040, 95%CI 1.009-1.063, P=0.010), while the application of statin played the role of an independent protective factor (OR=0.420, 95%CI 0.236-0.754, P=0.003). As for the simultaneous overgrowth of methane-producing and hydrogen-producing bacteria, increased BMI was found to be an independent protective factor (OR=0.870, 95%CI 0.786-0.964, P=0.008). In SIBO-positive group, it was found that for patients aged <45 years, both the methane-positive rate and the double-positive rate were significantly lower than the hydrogen positivity rate (P<0.05). Moreover, among patients aged 45-60 years, the double-positive rate was significantly lower than the hydrogen positivity rate (P<0.01). When it comes to the hydrogen-positive rate, it was significantly lower for patients aged 45-60 and 60-75 years compared with that of patients aged <45 years (P<0.05). In contrast, the methane-positive rate and the double-positive rate were significantly higher for patients aged 45-60 and 60-75 years than those of patients aged <45 years (P<0.01).ConclusionA history of coronary heart disease and increasing age are independent risk factors for intestinal hydrogen-producing bacterial overgrowth and methanogen overgrowth, respectively. The application of statins and increased BMI are independent protective factors for intestinal methanogen simultaneous overgrowth of methanogen and hydrogen-producing bacteria, respectively.

small intestinal bacterial overgrowth;breath test;intestinal methanogen overgrowth;hydrogen-producing bacterial overgrowth;age;coronary disease