Prevalence and predictors of small intestinal bacterial overgrowth in irritable bowel syndrome: a systematic review and meta-analysis

J Gastroenterol. 2018 Jul;53(7):807-818. doi: 10.1007/s00535-018-1476-9. Epub 2018 May 14.


Background: The reported prevalence of small intestinal bacterial overgrowth (SIBO) among individuals with irritable bowel syndrome (IBS) is highly variable. The aim of the study is to estimate the prevalence and identify predictors of SIBO in IBS.

Methods: PubMed, Cochrane Library, and EMBASE through July 2017 were searched to identify studies evaluating the prevalence of SIBO in IBS. The pooled prevalence of SIBO among individuals with IBS and the pooled odds ratio (OR) of SIBO among those with IBS compared with healthy controls were calculated. Predictors of SIBO among IBS patients were also evaluated.

Results: Fifty studies (8398 IBS, 1432 controls) met the inclusion criteria. Overall pooled prevalence of SIBO in IBS was 38% (95% CI 32-44) and was higher among individuals with IBS (OR 4.7, 95% CI 3.1-7.2) compared with controls. The pooled prevalence of SIBO in IBS was higher in studies diagnosed by breath tests (40%, 95% CI 33-46) compared with cultures (19%, 95% CI 8-30). Among those with IBS, female gender (OR 1.5, 95% CI 1.0-2.1), older age (standard mean difference 3.1 years, 95% CI 0.9-5.4), and IBS-diarrhea (OR 1.7, 95% CI 1.3-2.3) compared with other IBS subtypes increased the odds of SIBO; proton pump inhibitor (PPI) use (OR 1.1, 95% CI 0.7-1.7) was not associated with SIBO.

Conclusions: More than one-third of IBS patients tested positive for SIBO, and the odds of SIBO in IBS were increased by nearly fivefold. The prevalence of SIBO varied according to the diagnostic modality performed. Female gender, older age, and IBS-diarrhea, but not PPI use, were associated with SIBO among individuals with IBS.

Keywords: Breath test; Culture; Irritable bowel syndrome; Small intestinal bacterial overgrowth.

Publication types

  • Meta-Analysis
  • Systematic Review

MeSH terms

  • Adult
  • Age Factors
  • Bacterial Infections / diagnosis
  • Bacterial Infections / epidemiology*
  • Breath Tests
  • Diarrhea
  • Female
  • Humans
  • Intestine, Small / microbiology*
  • Irritable Bowel Syndrome / epidemiology*
  • Irritable Bowel Syndrome / microbiology*
  • Male
  • Middle Aged
  • Prevalence
  • Sex Factors