Background: A case definition of Gulf War illness with 3 primary variants, previously developed by factor analysis of symptoms in a US Navy construction battalion and validated in clinic veterans, identified ill veterans with objective abnormalities of brain function. This study tests prestated hypotheses of its external validity. Methods: A stratified probability sample (n = 8,020), selected from a sampling frame of the 3.5 million Gulf War era US military veterans, completed a computer-assisted telephone interview survey. Application of the prior factor weights to the subjects’ responses generated the case definition. Results: The structural equation model of the case definition fit both random halves of the population sample well (root mean-square error of approximation = 0.015). The overall case definition was 3.87 times (95% confidence interval, 2.61–5.74) more prevalent in the deployed than the deployable nondeployed veterans: 3.33 (1.10–10.10) for syndrome variant 1; 5.11 (2.43–10.75) for variant 2, and 4.25 (2.33–7.74) for variant 3. Functional status on SF-12 was greatly reduced (effect sizes, 1.0–2.0) in veterans meeting the overall and variant case definitions. Conclusions: The factor case definition applies to the full Gulf War veteran population and has good characteristics for research.
© 2011 S. Karger AG, Basel
- Epidemiological methods
- Case definition
- Diagnostic criteria
- Confirmatory factor analysis
- Health surveys
- Persian Gulf syndrome
- Validation studies
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Prof. Robert W. Haley, MD
Division of Epidemiology, Department of Internal Medicine
University of Texas Southwestern Medical Center
5323 Harry Hines Blvd, Dallas, TX 75390-8874 (USA)
Tel. +1 214 648 3075, E-Mail Robert.Haley@UTSouthwestern.edu
Received: June 7, 2011
Accepted: August 3, 2011
Published online: October 7, 2011
Number of Print Pages : 12
Number of Figures : 3, Number of Tables : 5, Number of References : 53
Vol. 37, No. 2, Year 2011 (Cover Date: October 2011)
Journal Editor: Feigin V.L. (Auckland)
ISSN: 0251-5350 (Print), eISSN: 1423-0208 (Online)
For additional information: http://www.karger.com/NED
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