Potential Link Between Functional Dyspepsia and Small Intestinal Bacterial Overgrowth

Researchers aimed to determine the role of small intestinal bacterial overgrowth in patients with functional dyspepsia.

There is a potential link between functional dyspepsia (FD) and small intestinal bacterial overgrowth (SIBO), according to a study published in The American Journal of Gastroenterology.

Several studies have reported an increased prevalence of SIBO in patients with FD. However, patients with FD are frequently treated with proton pump inhibitors, which are often considered a risk factor for SIBO by their impairing the acid barrier of the stomach. Thus, researchers performed a systematic review and meta-analysis to determine the role of SIBO in patients with FD.

Investigators identified 7 studies that included 263 patients with FD and 84 controls. They found that the odds for SIBO in patients with FD were significantly higher compared with that of controls, in 4 of these studies including 234 participants (odds ratio [OR], 4.3; 95% CI, 1.1–17.5); however, there was moderate heterogeneity in the analysis.

Including 3 high-quality, case-control studies with 200 participants (all using glucose breath tests [GBTs]), the risk of SIBO in patients with FD as compared with controls was higher (OR, 2.8; 95% CI, 0.8–10.0), with minimal heterogeneity in the analysis.

With use of lactulose breath tests in 3 studies with 110 participants, SIBO prevalence in FD was significantly higher (53.4%; 95% CI, 33.9–71.9) as compared with that of GBTs used in 4 studies with 153 participants (17.2%; 95% CI, 8.6–31.6). Substantial heterogeneity was found in studies using lactulose breath tests but not in studies using GBTs. There was also no significant difference in SIBO prevalence in patients with FD according to FD subtype.

The authors concluded that, “The quality of evidence is low and can be largely attributed to the type of breath test for SIBO diagnosis and clinical heterogeneity.” They added, “More appropriately designed studies are required to confirm the link between SIBO and FD.”


Gurusamy SR, Shah A, Talley NJ, et al. Small intestinal bacterial overgrowth in functional dyspepsia: a systematic review and meta-analysis. Am J Gastroenterol. 2021;116(5):935-942. doi: 10.14309/ajg.0000000000001197. PMID: 33734110