Canada deployed more than 4000 sea, land, and air troops to the gulf region; they participated in a naval blockade and were responsible for one-fourth of enemy interceptions in the gulf. A survey of the entire Canadian Gulf War force found that deployed veterans were at least five times as likely as nondeployed veterans to report symptoms of CFS (OR 5.27, 95% CI 3.95-7.03) (Goss Gilroy, 1998). Veterans were not interviewed or examined, and all data were obtained from self-reports. The CFS-like illness was based on responses to questions derived from the CDC criteria and a score above zero on the Chalder fatigue scale.4 With only minor modifications, the items used in this study were the same as those used by the Iowa Persian Gulf Study Group (1997). The study was limited by the lack of in-person interviews and examinations and by the nontraditional assessment of CFS.
The Iowa Persian Gulf study (1997) surveyed 1896 deployed and 1799 nondeployed veterans who listed Iowa as their home state at the time of enlistment. The presence of a CFS-like condition was based on a combination of symptoms used in the CDC criteria (Fukuda et al., 1994) and scores on the Chalder fatigue scale. The investigators found that the prevalence differed by 1.4% (95% CI 0.9-2.0) after adjusting for age, sex, race, branch of military, and rank. Study limitations were the use of self-reports of symptoms on a questionnaire and the lack of medical evaluations. Although rigorously conducted and analyzed, the study suffers shortcomings similar to those of the Canadian study.
The Update committee identified two new primary studies: Kelsall et al. (2006), who assessed health outcomes in Australian Gulf War veterans with chronic fatigue, and Ismail et al. (2008), who assessed UK Gulf War veterans for chronic fatigue and related disorders.
Between August 2000 and April 2002, Kelsall et al. (2006) conducted a cross-sectional study of chronic fatigue in male Australian Gulf War veterans. A total of 1456 deployed veterans participated (80.5% response rate of all who were deployed), and a comparison group consisted of 1588 individuals who served concurrently but were not deployed (56.8% response rate). Ascertainment was via a postal questionnaire plus a comprehensive medical evaluation that included neurologic and psychiatric tests, as well as the following laboratory tests: complete blood examination; erythrocyte sedimentation rate; urea; creatinine; electrolytes; serum calcium and phosphate; liver function tests; random plasma glucose; C-reactive protein; and serology tests (Epstein-Barr virus IgG, cytomegalovirus IgG, and hepatitis C core antibody). One percent of the Gulf War veterans and the comparison group had been diagnosed with CFS (adjusted OR 1.2, 95% CI 0.5-2.9). However, more Gulf War deployed veterans (7.9%) had prolonged fatigue lasting more than 6 months than did the comparison group (4.2%; aOR 1.9; 95% CI 1.4-2.7); and a similar increase was noted in the complaint of fatigue at all levels in the deployed group. In a small subset of controls who had been actively deployed elsewhere, the differences in complaints of chronic or prolonged fatigue were less apparent compared with the Gulf War deployed individuals and in fact failed to reach statistical significance; thus, there was an apparent active deployment effect. The odds of fatigue increased with reports of more PB tablets used, exposure to pesticides, belief in being near chemical weapons, and being in the gulf during air war. The strengths of this study are its relatively large size and national ascertainment. The weakness is