• Use of cross-sections, which limits assessment of symptom duration and chronicity, latency of onset, severity, and prognosis.

Virtually all the reports in the Gulf War and Health series have called for improved studies of Gulf War and other veterans. The Update committee reiterates that need but notes that it is difficult if not impossible 20 years after the war to reconstruct the exposures to which the veterans were subjected in theater or to establish years after deployment the predeployment physical and mental health status of the veterans for comparison purposes. Therefore, the committee believes that future studies of Gulf War veterans—and indeed any veteran population—need to be adequately designed to

  • Provide sufficient statistical power (precision).

  • Ensure validity, including the avoidance of such bias as response bias and recall bias, which lead deployed and nondeployed veterans to participate unequally, depending on general health and symptom presence and severity, or to report symptoms differently according to perceived exposures and health status.

  • Improve disease measurement to avoid misclassification; for example, including information collected from non-DoD hospitals in studies of hospitalization, obtaining cancer incidence data from existing cancer registries, validating self-reports of health outcomes, and using the least error-prone measures of these outcomes.

  • Characterize deployment and potential related adverse environmental influences better by, for example, collecting information on the length and location of deployment and on jobs and tasks.

  • Measure and adjust for possible confounding factors by, for example, measuring and adjusting for lifestyle factors (such as smoking and risk-taking behaviors) and predeployment physical and psychologic health status.

RECOMMENDATIONS

After almost two decades of research on Gulf War veterans, important questions about their health remain unanswered. In particular, the nature and extent of the multisymptom illness reported in the veterans warrant further research to refine its diagnosis and develop effective treatments. The committee believes that the path forward for veterans has two branches. The first is continued surveillance of deployed and nondeployed Gulf War veterans.

  • Although further investigations based solely on self-reporting are not likely to contribute substantially to the understanding of Gulf War illness, well-designed follow-up studies of mortality, cancer, neurologic, and psychiatric outcomes will continue to be valuable. Well-designed, adequately powered studies of MS and ALS incidence after deployment are also needed.

  • Methodologically robust cohorts need to be assembled and followed carefully to track the development of ALS, MS, brain cancer, psychiatric conditions, and health problems that occur at a later age, such as other cancers, cardiovascular disease, and neurodegenerative diseases. Several well-characterized cohorts that could form the basis of future studies have already been established, such as the US cohort studied by VA, the two UK cohorts, and the



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