than sufficient to meet the Rome III criteria for IBS and possibly other functional GI disorders (Drossman, 2006; Longstreth, 2006; Longstreth et al., 2006). For these reasons this study is considered to be primary.

An update of previous data by Gray and colleagues (2002) was a survey of nearly 12,000 active-duty Seabees, from 14 commands, still on active duty for at least 3 years after the Gulf War. The study subjects were queried about self-reported physician-diagnosed illnesses, symptoms, and exposures. IBS was one of the physician-diagnosed illnesses listed on the survey. Deployed Gulf War Seabees were much more likely than nondeployed Seabees to report being diagnosed with irritable bowel syndrome (2.48% vs 0.81%, OR 3.57, 95% CI 2.22-5.73). Irritable bowel syndrome was one of a cluster of four physician-diagnosed conditions—along with PTSD, chronic fatigue syndrome, and multiple chemical sensitivity syndrome—found to be more prevalent among Gulf War deployed Seabees than nondeployed Seabees, and these four conditions were highly associated with one another. Among the deployed Seabees, being diagnosed with one of these four conditions also was associated with reporting many other symptoms (16 other symptoms) whereas other deployed Seabees not reporting any of these four conditions had fewer (6) other symptoms. Because the focus of this study was to cluster symptoms and conditions that might shed light on a unique Gulf War illness, the analysis undertook no further evaluation of GI conditions in isolation.

Numerous studies have queried deployed and nondeployed US Gulf War veterans about gastrointestinal or stomach symptoms generally (Lindem et al., 2003a,b,c; Steele, 2000); they have also been asked about a number of specific gastrointestinal symptoms such as gas (Fukuda et al., 1998; Proctor et al., 1998), bloating (Fukuda et al., 1998), cramps (Fukuda et al., 1998; Proctor et al., 1998; Steele, 2000), abdominal pain (Fukuda et al., 1998; Knoke et al., 2000; Steele, 2000); diarrhea (Fukuda et al., 1998; Kang et al., 2000; Knoke et al., 2000; Proctor et al., 1998; Steele, 2000), constipation (Knoke et al., 2000; Proctor et al., 1998), loose bowel movements (Knoke and Gray, 1998), and nausea or upset stomach (Kroenke et al., 1998; Proctor et al., 1998; Steele, 2000). In all of these studies deployed veterans reported more GI symptoms than their nondeployed counterparts.

Kang et al. (2000) asked Gulf War veterans about whether they had any of three specific digestive conditions: gastritis, enteritis, or colitis. The sample included active-duty, reserve, and National Guard personnel as well as an oversampling of female veterans who were in the military between September 1990 and May 1991. The prevalence of gastritis was more than doubled in the deployed veterans compared with the nondeployed veterans (25% vs 12%). In 2004-2005, Kang et al. (2009) conducted a follow-up study of the 15,000 deployed and 15,000 nondeployed veterans originally surveyed in 1995 (Kang et al., 2000). Veterans were asked via a mailed questionnaire if their doctor had ever told them they had any of 23 medical conditions, including gastritis and irritable bowel syndrome. Both gastritis and IBS were among the top five medical conditions with the greatest relative risk; the relative risk was 1.52 (95% CI 1.40-1.65) for gastritis and 1.50 (95% CI 1.35-1.66) for IBS, adjusted for age, sex, race, body mass index, current cigarette smoking, rank, branch of service, and unit component. This study is limited by the use of a self-report survey, and indeed gastritis using symptom reports is more likely to be functional dyspepsia. Because the questionnaire items were not sufficiently detailed to make a diagnosis of a functional digestive disorder (via Rome criteria) or to identify structural disorders by endoscopy, this study is considered to be secondary.

Surveys of deployed Gulf War troops from other countries showed similar results to those of the Danish veterans (Ishoy et al., 1999a,b). UK Gulf War veterans self-reported more

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