ABSTRACT
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.
Subject(s)
Gulf War , Models, Statistical , Persian Gulf Syndrome/epidemiology , Population Surveillance/methods , Surveys and Questionnaires/standards , Veterans , Female , Humans , Male , Middle Aged , Persian Gulf Syndrome/diagnosis , Random Allocation , United States/epidemiologyABSTRACT
The past 20 years have seen an overall decline in survey response rates and an even more pronounced decline in samples of health care professionals. The authors tested the use of a "thank you" or "reminder" postcard as a method by which to stem the tide of declining response rates. The authors conducted a mail and telephone survey of 49,605 registered nurses for the 2000 National Sample Survey of Registered Nurses and sent an extra mailing to a random subsample (n = 4,968). They then compared response rates for both groups. Contrary to prior research, this study found that reminder postcards did not improve response rates or rates of return. There may be several reasons for this finding, including the general familiarity with, and high saliency of, this research project for the nursing community. These results suggest that even widely accepted best practices for survey methods deserve scrutiny when applied to special subpopulations.
