IBS after wartime exposure (Tuteja et al., 2008; Wurzelmann et al., 2008) as well as one published study of increased adult Rome III-diagnosed IBS incidence rates that related to severe early-life wartime exposure during World War II (Klooker et al., 2009).

GI diseases, sometimes called “organic” or structural diseases, such as peptic ulcer and inflammatory bowel disease (that is, ulcerative colitis and Crohn’s disease), are characterized by morphological abnormalities seen on x-ray, endoscopy, or through laboratory tests. For example, with Crohn’s disease the intestine may be inflamed and have ulcerations, strictures, fistulas, or abscesses. The diagnoses of these diseases need to be validated by medical records since some physicians may place an organic label on the patient’s symptoms (such as gastritis or peptic ulcer) but without proper morphological correlation. Such labeling will confound the diagnosis of these diseases when surveys are used, particularly when the data are based on the individual’s recollection of a physician’s diagnosis.

For the purposes of this section, the committee defined primary studies by their methodological rigor (see Chapter 2) and outcome assessment requiring sufficiently valid symptom clusters consistent with a functional GI diagnosis, or in the case of structural diseases, physical examination. The primary studies are summarized in Table 4-9.

Summary of Volume 4

Primary Studies

In Volume 4, three studies were identified that met that committee’s criteria for primary studies: Eisen et al. (2005), who conducted a survey and physical examinations, and two hospitalization studies by Gray et al. (1996, 2002).

Ten years after the Gulf War, in the National Health Survey of Gulf War Era Veterans and Their Families, a nationally representative population-based study, the VA conducted medical evaluations to determine the prevalence of common diseases in deployed veterans (Eisen et al., 2005). In 1999-2001, 1061 deployed and 1128 nondeployed veterans were evaluated at several VA centers. The veterans had been randomly selected from 11,441 deployed and 9476 nondeployed veterans who had participated in a 1995 VA survey (Kang et al., 2000) that used a self-report questionnaire. Dyspepsia was diagnosed through in-person interviews according to two criteria: a history or symptoms of dyspepsia (frequent heartburn and recurrent abdominal pain) and use of antacids, histamine-2 receptor blockers, or other medications to treat dyspepsia. The prevalence of dyspepsia was 9.1% and 6.0% in deployed and nondeployed veterans, respectively (OR 1.87, 95% CI 1.16-2.99). Reports of gastritis were 5.9% and 4.2%, respectively (OR 1.57, 95% CI 0.88-2.78). Study limitations for these outcomes are: dyspepsia was diagnosed crudely as recurrent abdominal pain or frequent heartburn, which is more commonly associated with gastroesophageal reflux disease; IBS, a more common functional GI disorder, was not evaluated; and despite three recruitment waves, participation was only 53% of eligible Gulf War and 39% of eligible nondeployed veterans.

A study by Gray et al. (1996) showed no excess hospitalizations in DoD hospitals for digestive system disorders, as broadly defined by a range of ICD codes, from 1991 to 1993. That study compared hospitalizations of almost 550,000 Gulf War veterans and almost 620,000 nondeployed veterans who remained on active duty until 1993. Another further hospitalization study conducted by Gray et al. (2000) covered the years 1991-1994 and examined DoD, VA, and California hospitals. The study examined hospitalizations at nonfederal hospitals in California to eliminate potential bias related to veterans seeking care outside DoD and VA facilities.

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