A major population-based study of US veterans was mandated by Public Law 103–446. It is a retrospective cohort study conducted by VA. Its purpose is to estimate the prevalence of symptoms and other health outcomes in Gulf War veterans versus non-Gulf War veterans.¹¹ This population-based survey had three phases. The first phase was a questionnaire mailed to 30,000 veterans. The second phase validated self-reported data with medical-record review and analyzes characteristics of those who did not respond to the mailed survey. The third phase is a comprehensive medical examination and laboratory testing of a random sample of 2000 veterans drawn from both the Gulf War and the comparison group (Research Working Group, 1998). The purpose of the third phase is to establish diagnoses that will make it possible to see what proportion of self-reported symptoms are due to established diseases rather than unexplained illnesses. The findings of only the first two phases have been published.

The study was designed to be representative of the nearly 700,000 US veterans sent to the Persian Gulf and 800,680 non-Gulf veterans of the same era. Questionnaires were mailed to a stratified random sample of 15,000 Gulf War and 15,000 non-Gulf War veterans identified by DOD and representing various military branches and units. The questionnaires contained a list of 48 symptoms and questions about chronic medical conditions, functional limitations, and other items from the National Health Interview Survey. A questionnaire about exposures was also included. The response rate was about 70%.

The investigation found significantly higher symptom prevalence of all 48 symptoms among Gulf War veterans (Kang et al., 2000). Four of the 10 most frequently reported symptoms are runny nose, headache, unrefreshing sleep, and anxiety (Table A.5). Numerous chronic medical conditions—such as sinusitis, gastritis and dermatitis—were reported more frequently among Gulf War veterans; many were reported twice as often. Ten symptoms and 12 medical conditions were remarkably similar in prevalence to those in a UK cohort (Unwin et al., 1999). Finally, Gulf War veterans reported significantly higher rates of functional impairment (27.8% versus 14.2%), limitations of employment (17.2% versus 11.6%), and health-care use, as assessed by clinic visits (50.8% versus 40.5%) or hospitalizations (7.8% versus 6.4%). In a randomly selected subset of veterans, medical-record reviews verified more than 90% of self-reported reasons for clinic visits or hospitalizations.