To the Editor.
—In the 3-part study of a reserve naval mobile construction battalion by Dr Haley et al,1-8 the hypothesis that wartime exposure to combinations of chemical agents caused neurologic injury among Gulf War veterans cannot be supported because of methodological limitations and the need for further clarification and analysis. The possibility of both selection and recall bias is an underlying limitation of all 3 studies because the initial population survey,1 which categorized 63 veterans into 6 syndromes by factor analysis, relied on selfreported symptoms provided by a minority of eligible participants. Further analysis of potential biases is needed, including the reasons provided for nonparticipation.1 In addition, the case definition of unexplained illnesses developed for the Department of Defense in 1994 does not provide a basis for comparison of the postulated syndromes.1 This working definition was developed from the most common self-reported symptoms of a unique population (self-referred clinic
Hyams KC, Wignall FS. Identification of Gulf War Syndrome: Methodological Issues and Medical Illnesses. JAMA. 1997;278(5):384. doi:10.1001/jama.1997.03550050046021