matic stress disorder (PTSD), sexual discomfort, or chronic fatigue (Table 2.4).10 Furthermore, on a standardized instrument for assessing functioning (the Medical Outcome Study’s 36-item questionnaire known as the Short Form-36, or SF-36), Gulf War veterans displayed significantly lower scores across all eight subscales for physical and mental health. These subscales profile different aspects of quality of life. The subscales for bodily pain, general health, and vitality showed the greatest absolute differences between deployed and nondeployed veterans. In short, this large, well-controlled study demonstrated that certain sets of symptoms are more frequent and quality of life is poorer among Gulf War veterans than among nondeployed military controls.
Symptom clustering. The Iowa study was the first major population-based study to group together sets of symptoms into categories suggestive of existing syndromes or disorders, such as fibromyalgia or depression. The Iowa study did not search for new syndromes. However, its finding of such higher prevalence of symptom groups suggestive of fibromyalgia, depression, and cognitive dysfunction (see Table 2.4) motivated subsequent researchers to examine the potential for a new syndrome that would group together and classify veterans’ symptoms.
Exposure–symptom relationships. The Iowa study assessed exposure– symptom relationships by asking veterans to report on their past exposures. Researchers found that many of the self-reported exposures were significantly associated with many different health conditions. For example, symptoms of cognitive dysfunction were found to have been associated with self-reports of exposure to solvents or petrochemicals, smoke or combustion products, sources of lead from fuels, pesticides, ionizing or nonionizing radiation, chemical warfare agents, use of pyridostigmine, infectious agents, and physical trauma. A similar set of exposures also was associated with symptoms of depression or fibromyalgia. The study concluded that no single exposure to any specific agent was related to the conditions that the authors found to be more prevalent in Gulf War veterans.
The findings of a 1997 survey mailed to the entire cohort of Canadian Gulf War veterans were similar to those from the Iowa study. In this study, Canadian forces deployed to the Gulf War (n = 3,113) were compared with Canadian forces deployed elsewhere (n = 3,439) during the same period (Goss Gilroy, 1998). Of the Gulf War veterans responding, 2,924 were male and 189 were female. Deployed forces had significantly higher rates than controls of self-
The conditions listed were not diagnosed because no clinical examinations were performed. Rather, before conducting their telephone survey, researchers grouped together sets of symptoms from their symptom checklists into a priori categories of diseases or disorders. After a veteran identified him- or herself as having the requisite set of symptoms, researchers analyzing responses considered the veteran as having symptoms “suggestive” of or consistent with a particular disorder, but not as having a formal diagnosis of the disorder.