that the exposure and symptom history was ascertained by self-report, raising a substantial possibility of biased recall.

Ismail et al. (2008) reported the prevalence of CFS and related disorders in UK veterans of the Gulf War. In this two-phase cohort study, randomly selected subsamples from a population-based cross-sectional postal survey of more than 10,000 military personnel were compared with control groups that included Bosnian peacekeepers and nondeployed military personnel. Comparisons were matched for total level of disability using a physical functioning scale. Gulf War veterans were more likely to be overweight, to be hypertensive, and to have elevated serum transaminase (AAT) levels. (It is possible that the AAT levels may reflect being overweight.) Among the disabled veterans, the adjusted OR for CFS was 7.8 (95% CI 2.5-24.5). CFS was present in 18% of disabled Gulf War veterans compared with only 3% of disabled nondeployed veterans. Remarkably, rates for other medically explainable conditions were not increased, indicating that the CFS symptoms were specifically increased in the Gulf War deployed population. Over half of veterans satisfying criteria for CFS had concomitant depression or anxiety disorder. The authors concluded that CFS was a medically unexplained condition associated with Gulf War service.

The Update committee identified one new secondary study. Lucas et al. (2007) administered a questionnaire about wartime exposures and symptoms experienced in 49 Gulf War veterans complaining of chronic fatigue matched to 44 healthy controls who were also deployed. For the purposes of the study, fatigue had to begin by July 1992. Fatigue was associated with exposure to oil fire, smoke, pesticides, contaminated food or water, Scud missiles, dead bodies, dead animals, and other environmental agents. There was also an association of fatigue with use of PB that increased 1.3% with every pill taken; there were also general trends toward worse health with PB exposure. This study was markedly limited by a very small sample size and a small number of individuals with PB intake data. There was also no adjustment made for multiple comparisons.

Summary and Conclusions

CFS and complaints of unexplained chronic fatigue appear to be increased in deployed Gulf War veterans compared to contemporaneous cohorts (either nondeployed or deployed elsewhere). This has been observed in several cross-sectional population-based studies that used self-reports to define CFS or chronic fatigue. However, the absolute prevalence of these symptoms has varied considerably from study to study. Associations between fatigue, subjective neurological symptoms, and exposures are also based entirely on retrospective self-reports.

Therefore, the committee concludes that there is a sufficient evidence for an association between deployment to the Gulf War and chronic fatigue syndrome. The underlying basis of the possible relationship is unclear, however, and further research is recommended.

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