Impact of small intestinal bacterial overgrowth on symptoms and quality of life in irritable bowel syndrome

OBJECTIVE: To explore the factors associated with small intestinal bacterial overgrowth (SIBO), and to further evaluate the impact of SIBO on irritable bowel syndrome (IBS) in terms of symptom severity and health-related quality of life (HRQoL).

METHODS: A cross-sectional study of consecutive adult patients who underwent glucose hydrogen breath test was conducted. Factors associated with SIBO were evaluated. Symptom severity and HRQoL of IBS patients with and without SIBO were compared. The independent factors associated with severe IBS were explored.

RESULTS: A total of 160 patients were included (median age 40 years, males 31.3%). IBS was present among 53.8% of subjects, with 33.8% having diarrhea-predominant IBS (IBS-D). SIBO was diagnosed in 22.5% of the study population. Patients with SIBO were more commonly diagnosed with IBS-D than those without (50.0% vs 29.0%, P = 0.019). Severe IBS was associated with SIBO (36.4% vs 15.6%, P = 0.043). SIBO was associated with poorer HRQoL (Euroqol five-dimensional utility score: 0.73 vs 0.80, P = 0.024). SIBO (44.4% vs 20.6%, P = 0.043), anxiety (77.8% vs. 39.7%, P = 0.004), and depression (50.0% vs 19.1%, P = 0.011) were associated with severe IBS in the univariate analysis. However, SIBO was the only independent factor associated with severe IBS in the multivariate analysis (adjusted odds ratio 3.83, 95% confidence interval CI 1.02-14.34, P = 0.046).

CONCLUSIONS: There was a significant association between IBS-D and SIBO. The coexistence of SIBO had a significant negative impact on IBS patients.