Gulf War Digestive Health Study

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US Department of Veterans Affairs (VA)




Irritable Bowel Syndrome
Small Intestinal Bacterial Overgrowth


Drug: Placebo
Drug: Rifaximin

Study type


Funder types

Other U.S. Federal agency



Details and patient eligibility


The purposes of this study are to estimate the burden of disease due to chronic gastrointestinal illness in PG veterans, to evaluate whether Small Bowel Bacterial Overgrowth (SBBO) is associated with chronic diarrhea in PG veterans, and to determine whether eradication of SBBO reduces symptoms of chronic diarrhea, abdominal pain and bloating in PG veterans.

Full description

Approximately 700,000 United States military personnel were deployed in the first Persian Gulf (PG) War. Several months after their return, up to 25% of Veterans had persistent symptoms which they suspected were related to their military service in the Gulf. Among the most frequent were gastrointestinal symptoms such as loose stools, excessive gas and abdominal pain. These symptoms are typical of diarrhea-predominant irritable bowel syndrome (IBS). The cause of IBS is not known; speculated mechanisms include altered GI motility, bacterial overgrowth, visceral hypersensitivity and psychological stress. Another proposed mechanism relates to the fact that up to one third of patients with IBS describe the onset of their symptoms following acute gastroenteritis. This is called post-infective IBS (PI-IBS). How acute gastroenteritis leads to persistent GI symptoms of IBS is not known. A limited amount of data suggests that patients with IBS may have an imbalance in their gastrointestinal microflora. Several studies indicate that small bowel bacterial overgrowth is more common in individuals with IBS. Symptoms of SBBO are similar to diarrhea-predominant IBS and include chronic diarrhea, bloating and abdominal pain. More than 50 percent of military personnel developed acute gastroenteritis while on duty in the Gulf. Most of them who reported symptoms of IBS had an acute onset which occurred in association with an episode of acute gastroenteritis during their tour of duty. Other travelers are known to be colonized by new micro-organisms during travel to foreign countries. This acquisition is thought to be related to a change in diet. The natural history of this change in bowel flora, in part, depends on host factors and can persist for months after travel abroad. It seems likely, that PG veterans with persistent diarrhea and a negative work-up for known GI diseases have PI-IBS. No study in the past has evaluated the role of SBBO in causing chronic GI symptoms in PG Veterans. Furthermore, soldiers involved in combat are exposed to a highly stressful environment, perhaps making them more susceptible to persistent symptoms. We hypothesize that PG veterans with chronic GI symptoms have symptoms of diarrhea predominant IBS and this is caused by SBBO due to a change in microflora during deployment in the Persian Gulf and that it is predisposed to by the stress of combat. Intestinal microflora, once altered, is known to be relatively stable; once mucosal damage occurs it may become permanent. Objectives Objective # 1: Estimate the burden of disease due to chronic gastrointestinal illness in PG veterans. Hypothesis: i. The prevalence of GI symptoms is high in PG veterans. ii. The prevalence of IBS is higher in veterans who report acute gastroenteritis during the period of deployment. iii. PG Veterans with IBS have a lower IBS related QOL Objective # 2: Evaluate whether SBBO is associated with chronic diarrhea in PG veterans. Hypothesis i. SBBO is more common in PG veterans than non deployed veterans. ii. SBBO is more common in PG veterans with diarrhea-predominant IBS vs. those without. Objective: # 3: Determine whether eradication of SBBO reduces symptoms of chronic diarrhea, abdominal pain and bloating in PG Veterans. Hypothesis: i. Treatment with rifaximin, a non-absorbable antibiotic, will improve symptoms and QOL in Veterans with SBBO.


54 patients




35 to 72 years old


No Healthy Volunteers

Inclusion criteria

  • Men and women age 32-75 years
  • Rome III criteria for diarrhea-predominant IBS
  • Symptom onset after an apparent episode of acute gastroenteritis
  • Symptoms of > 3 months duration
  • Normal endoscopic appearance of the colonic mucosa
  • Negative markers for celiac disease and inflammatory bowel disease.
  • Normal thyroid function and serum calcium levels.
  • Must have served in the military or reserves during the time of Operation Desert Storm (August 1990 to May 1991)

Exclusion criteria

  • Clinically significant cardiac, pulmonary, hepatic or renal dysfunction
  • History of/or presence of systemic malignancy
  • Current evidence of any gastrointestinal disorder such as celiac disease or inflammatory bowel disease (i.e. Crohns disease or ulcerative colitis)
  • Current effects of drug or alcohol abuse
  • Investigator perception of patients inability to comply with study protocol
  • Unstable psychiatric disease
  • Recent change in gastrointestinal medications
  • Subjects with a positive pregnancy test
  • Subject is currently participating in another research protocol that could interfere or influence the outcome measures of the present study

Trial design

Primary purpose




Interventional model

Parallel Assignment


Triple Blind

54 participants in 2 patient groups, including a placebo group

Treatment Group
Active Comparator group
These patients have IBS and are receiving the rifaximin.
Drug: Rifaximin
Placebo group
Placebo Comparator group
These patients have IBS and are receiving the placebo.
Drug: Placebo

Trial contacts and locations



Data sourced from

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