transportation accidents in the years immediately after the war and possibly were at increased risk for amyotrophic lateral sclerosis (ALS), and in one study deployed veterans’ offspring were more likely to have birth defects. Objective measures failed to show an increased prevalence of hospitalizations, cancer (results for testicular cancer were inconsistent), peripheral neuropathy, cardiovascular disease, diabetes, or pulmonary function in active-duty Gulf War veterans. The committee noted that few studies attempted to link specific exposures, such as exposure to oil-well fire smoke and possibly nerve agents released at Khamisiyah, to health outcomes. Only self-reports of exposure to oil-well fires were linked to an increase in self-reported respiratory symptoms that were suggestive of asthma and bronchitis.
The Update committee sought to characterize and weigh the strengths and limitations of the available evidence presented in the studies that it reviewed. For Volume 4 of the Gulf War and Health series, numerous cohort studies and case control studies were objectively reviewed without preconceptions about health outcomes that might be seen in Gulf War veterans. The Volume 4 committee developed criteria to determine which studies to include in its review. The Update committee reviewed and used those criteria to evaluate the studies that have been published since Volume 4 and also uses categories of association to determine the strength of associations between deployment to the Gulf War and health outcomes. The categories of association have been used by the other reports in the Gulf War and Health series.
To be a primary study, which would be used by the committee to support its conclusions, a study needed to demonstrate rigorous methods (for example, to be published in a peer-reviewed journal, to include details of methods, to have a control or reference group, and to include adjustments for confounders if needed), needed to include information regarding a persistent health outcome, needed to have a medical evaluation conducted by a health professional, and needed to use laboratory testing as appropriate. Those types of studies constituted the committee’s primary literature. The committee did not evaluate studies of acute trauma, rehabilitation, medical treatment, or transient illness.
Studies reviewed by the committee that did not necessarily meet all the criteria of a primary study were considered secondary studies. Secondary studies are typically not as methodologically rigorous as primary studies and might present subclinical findings; that is, they are studies of altered functioning consistent with later development of a diagnosis but without clear predictive value.
The present report excludes studies of participants in Gulf War registries established by VA or the Department of Defense (DoD), such as DoD’s Comprehensive Clinical Evaluation Program. Registry participants cannot be considered representative of all Gulf War veterans in that they are self-selected subjects, many of whom have joined the registries because they believe that they have symptoms of a new medical syndrome; in addition, they were not randomly selected from all Gulf War military personnel, and there is no nondeployed control group.