SIBO Facts and Statistics: What You Need to Know

The gut microbiota is the bacteria, viruses, and other organisms that normally live inside the digestive tract. When the amount of bacteria in the small intestine grows too large, or an abnormal type of bacteria grows there, it is called small intestinal bacterial overgrowth (SIBO).

It's not clear how many people are affected by SIBO, but it can result from certain other conditions. This article will review facts and statistics for small intestinal bacterial overgrowth.

Person experiencing intestinal discomfort, sitting on bed

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SIBO Overview

SIBO may occur in people who have had surgery on their bowels, take certain medications, or live with certain medical conditions affecting the digestive system. There is no one standardized way to test or treat SIBO. In some cases, it may be diagnosed with a breath test and treated with antibiotics.

Some of the signs and symptoms of SIBO include:

  • Abdominal bloating
  • Abdominal pain
  • Constipation
  • Dyspepsia (indigestion)
  • Gas and flatulence
  • Diarrhea
  • Fatigue
  • Malabsorption (not absorbing nutrients properly)
  • Nausea
  • Vitamin deficiencies (including iron)
  • Weight loss

How Common Is SIBO?

SIBO is considered a common condition, but no reliable data exist on how many people are diagnosed and treated yearly. However, there is some information available on how often SIBO affects people with other digestive conditions.

One study found that for people with inactive Crohn's disease (meaning that various clinical tests showed no sign of disease activity in people previously diagnosed with the condition), 16.8% had SIBO. Crohn's disease is an inflammatory bowel disease (IBD) that affects the lining of the digestive tract.

Another small study looked at the rate of SIBO in people who have celiac disease (an autoimmune condition triggered by gluten) and those who have irritable bowel syndrome (IBS), an intestinal disorder causing cramps, pain, diarrhea, and gas, compared to people without a digestive condition. It showed that in those with celiac disease, 13% had SIBO, and in people with IBS, 67% were diagnosed with SIBO.

SIBO by Ethnicity

There is little data on the prevalence of SIBO across ethnicities in the United States. However, studies in different countries or areas of the world that include people with IBS show various rates of SIBO in those populations.

The rates of SIBO in people with IBS across studies are:

  • Canada: 10%
  • Europe: 23%
  • India: 14%
  • Iran: 37%
  • Southeast Asia: 37%
  • United States: 55% 

SIBO by Age and Gender

Not much is known about how many people are affected by SIBO. Not only is it a condition related to other disorders, but there’s also not complete agreement among healthcare providers on how to diagnose and treat it.

What has been shown is that anywhere from 13% to 35% of healthy people may have SIBO, depending on which test is used to diagnose the condition. Older people may be at greater risk for SIBO because they tend to have altered levels of gastric acid and may be more likely to receive a medication that increases the risk of SIBO.

Causes of SIBO and Risk Factors

SIBO might occur when the balance of the microbiome in the small bowel is disturbed by something. This can happen because of a disease, condition, medication, or surgery that affects the bowels. It can also occur with conditions that don't directly affect the small bowel but may change the ability of the gut to regulate itself.

Several conditions are associated with SIBO. Some of the more common ones include:

  • Celiac disease: An autoimmune condition in which gluten protein in food triggers a reaction that damages the lining of the small intestine
  • Cirrhosis: Scarring of the liver caused by injury or disease
  • Crohn's disease: Inflammation and ulcers in the lining of the digestive tract
  • Diabetes: Inability of the body to manage blood sugar levels
  • Gastroparesis: A disorder that causes delayed emptying of the stomach
  • Hypothyroidism (underactive thyroid): A condition in which the thyroid gland doesn't produce enough hormones
  • IBS: A disorder of the gut-brain axis that causes symptoms in the lower digestive system
  • Obesity: A condition of having excess body fat and various other signs and symptoms
  • Radiation enteritis: A complication of radiation therapy that causes diarrhea and other symptoms in the lower digestive tract

Medications might also be a risk factor or a cause of SIBO. Medications that are associated with SIBO include:

  • Anticholinergics: Medications that slow the contractions of smooth muscles
  • Opioids: Pain medications that affect the digestive system
  • Proton pump inhibitors: Used to treat heartburn or gastroesophageal reflux disease (GERD) 

What Are the Mortality Rates for SIBO?

SIBO tends to be a complicating factor that goes along with other conditions. For that reason, it's not considered a fatal disorder. But it is possible that it leads to worse outcomes for people already managing certain serious conditions. 

For instance, one study on people with heart failure—a condition in which the heart doesn't pump enough blood to meet the body's needs—showed that SIBO is common and increases poor outcomes, like being readmitted to the hospital or risk of death. The authors of this study suggest that it's worth treating SIBO in people with heart failure. 

However, there's little other data to guide decisions on who should be tested and treated for SIBO and how it might affect the risks of complications. The decision to test and treat for SIBO will be made between healthcare providers and patients.

Screening and Early Detection for SIBO

It can be challenging to diagnose SIBO because there are no accepted guidelines on who to test for SIBO and when. It is known that SIBO is common in people with certain conditions, such as those who live with Crohn’s disease or IBS.

However, many of the symptoms of SIBO are nonspecific and are similar to the symptoms of other conditions. People may need to talk with a healthcare provider about additional testing if a condition is being treated, but symptoms such as bloating, pain, and diarrhea are not improving.

Some of the ways to test for SIBO include:

  • Breath tests, which are noninvasive and measure the hydrogen level during exhalation
  • Jejunal aspiration, which takes place during an endoscopy (in which a flexible tube is inserted into the body to take images)
  • Trialing a medication to treat SIBO and tracking results 

Summary

SIBO is a common condition, but how many people it affects is still not well understood. It can result as a complication of various other diseases and conditions. People may want to seek a diagnosis or treatment if they are in a higher risk group and suspect SIBO. 

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Rezaie A, Pimentel M, Rao SS. How to test and treat small intestinal bacterial overgrowth: An evidence-based approach. Curr Gastroenterol Rep. 2016;18:8. doi:10.1007/s11894-015-0482-9. 

  2. Lasa JS, Zubiaurre I, Fanjul I, Olivera P, Soifer L. Small intestinal bacterial overgrowth prevalence in celiac disease patients is similar in healthy subjects and lower in irritable bowel syndrome patients. Rev Gastroenterol Mex. 2015;80:171-174. doi:10.1016/j.rgmx.2015.04.002. 

  3. Shah A, Talley NJ, Jones M, et al. Small intestinal bacterial overgrowth in irritable bowel syndrome: A systematic review and Meta-analysis of case-control studies. Am J Gastroenterol. 2020;115:190-201. doi:10.14309/ajg.0000000000000504. 

  4. Sachdev AH, Pimentel M. Gastrointestinal bacterial overgrowth: pathogenesis and clinical significance. Ther Adv Chronic Dis. 2013;4:223-231. doi:10.1177/2040622313496126. 

  5. Quigley EMM, Murray JA, Pimentel M. AGA Clinical practice update on small intestinal bacterial overgrowth: Expert review. Gastroenterology. 2020;159:1526-1532. doi:10.1053/j.gastro.2020.06.090. 

  6. Song Y, Liu Y, Qi B, et al. Association of small intestinal bacterial overgrowth with heart failure and its prediction for short-term outcomes. J Am Heart Assoc. 2021;10:e015292. doi: 10.1161/JAHA.119.015292. 

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