effects with specific exposures, such as oil-well fire smoke or nerve gas agents, those studies were also considered.

COMMITTEE’S APPROACH TO ITS CHARGE

The committee began its evaluation by holding two public sessions. At those sessions, the committee heard from the VA and from Gulf War veterans about health outcomes that had been identified in Gulf War veterans during the past 20 years. During the second public session, the committee also heard presentations about health outcomes that were of particular concern to female veterans, a presentation from the chair of the IOM committee that had prepared Gulf War and Health, Volume 4, and from representatives of the VA Research Advisory Committee on Gulf War Veterans’ Illnesses, who discussed that committee’s findings and recommendations. Those sessions helped the committee to put its efforts in context and to clarify an approach to its task. The committee sought to characterize and weigh the strengths and limitations of the available evidence. It did not address policy issues, such as decisions regarding the potential costs of compensation.

Extensive searches of the epidemiologic literature published since 2005 were conducted using the same search strategy as that used for Volume 4; over 1000 potentially relevant references were retrieved. After an assessment of the titles and abstracts of the initial searches, the committee focused on some 400 potentially relevant epidemiologic studies for review and evaluation.

The committee adopted a policy of using only peer-reviewed published literature as the basis for its conclusions, with the exception of some government reports. The process of peer review by fellow professionals increases the likelihood of high quality but does not guarantee the validity of a study or the ability to generalize its findings. Accordingly, committee members read each study critically and considered its relevance and quality. The committee did not collect original data, nor did it perform any secondary data analysis.

To be comprehensive in its approach to the epidemiologic literature, the committee also reviewed the studies that had been included in Volume 4 as primary or secondary studies. The Volume 4 committee did not draw conclusions as to the strength of association between an exposure, that is, deployment to the Gulf War, and a particular health effect. However, Volume 4 did indicate what health outcomes had a greater prevalence in deployed veterans compared with nondeployed veterans. The Update committee has been asked to make a determination on the strength of the association between being deployed to the Gulf War and specific health effects. To make such a determination, the committee needed to review the studies cited in Volume 4 to assess whether those studies would still be classified as primary or secondary. The committee then considered the epidemiologic studies identified in the updated literature search. These studies were also reviewed and classified as primary or secondary according to the criteria discussed below and in more detail in Chapter 2. Once the committee had assessed the studies cited in Volume 4 and evaluated the new studies identified from the updated literature, it reviewed the entire body of relevant literature using a weight-of-the-evidence approach and determined the strength of the association between being deployed to the Gulf War and a specific health outcome based on the primary studies and supported by the secondary studies.



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