In Volume 4, the Iowa Persian Gulf Study was presented as the reference study with eight derivative studies. The Update committee identified three new studies derived from the original Iowa cohort.
The Iowa study was a cross-sectional survey of a representative sample of 4886 military personnel who listed Iowa as their home of record at the time of enlistment and served between August 2, 1990, and July 31, 1991 (Iowa Persian Gulf Study Group, 1997). The DMDC identified 29,010 potentially eligible military personnel; 42 records were not included for a variety of reasons including incomplete data or duplicate records, leaving a representative sample of 28,968.
Study subjects were divided into four groups: Gulf War-deployed active duty, Gulf War-deployed National Guard or reserve, Gulf War nondeployed active duty, and Gulf War nondeployed National Guard or reserve; samples were evenly selected from each of the four domains. A total of 4886 study subjects were randomly selected from the four groups; of the study subjects who were contacted, 3695 (76%) completed a telephone interview. Trained examiners used standardized questionnaires, instruments, and scales to collect information from the subjects. Sources of questions included the National Health Interview Survey, the Behavioral Risk Factor Surveillance Survey, the National Medical Expenditures Survey, the Primary Care Evaluation of Mental Disorders, the Brief Symptom Inventory, the CAGE questionnaire (for alcoholism),3 the PTSD (Posttraumatic Stress Disorder) Checklist—Military, the Centers for Disease Control and Prevention Chronic Fatigue Syndrome Questionnaire, the Chalder Fatigue Scale, the American Thoracic Society questionnaire, and the Sickness Impact Profile. The conditions listed were not diagnosed, because no clinical examinations were performed. Rather, before conducting their telephone survey, researchers grouped sets of symptoms from their symptom checklists into a priori categories of diseases or disorders. After a veteran identified himself 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.
Gulf War veterans scored significantly lower on all eight subscales for physical and mental health on the SF-36. The subscales for bodily pain, general health, and vitality showed the greatest absolute differences between deployed and nondeployed veterans. The Iowa study assessed exposure–symptom relationships by asking veterans to report on their deployment exposures including to solvents or petrochemicals, smoke or combustion products, lead from fuels, pesticides, ionizing or nonionizing radiation, chemical warfare agents, PB use, infectious agents, and physical trauma. The authors concluded that no exposure to any single agent was related to the medical conditions found to be more prevalent in Gulf War veterans (Iowa Persian Gulf Study Group, 1997).