This section contains an overview and update on neurocognitive and neurobehavioral performance in Gulf War veterans compared with nondeployed veterans. In Gulf War and Health, Volume 4: Health Effects of Serving in the War the committee defined primary studies as “high-quality studies that used neurobehavioral tests that had previously been used to detect adverse effects in population-based research on occupational groups.” Furthermore the committee presented findings separately for those studies that (a) compared neurobehavioral performance in deployed veterans and nondeployed veterans, and (b) compared neurobehavioral performance in deployed veterans reporting symptoms that met various definitions of Gulf War syndrome with neurobehavioral performance in deployed veterans who did not report symptoms.

The major issues that distinguished secondary studies from primary studies were lack of adjustment for potential confounding effects of age, sex, education, native intellectual ability (as measured by the Wechsler Adult Intelligence Scale, National Adults Reading Test [NART], Armed Forces Qualifying Test [AFQT]), and lack of blinding of testers to deployment and/or symptom status. Studies in which neurocognitive and neurobehavioral performance was measured only based on self-report were not included. Table 4-5 summarizes the primary studies for neurocognitive and neurobehavioral outcomes.

Summary of Volume 4

Studies in Nonsymptomatic Veterans

In consideration of the comparison of neurobehavioral performance in Gulf War deployed veterans compared with nondeployed veterans there were two primary studies (David et al., 2002; Proctor et al., 2003) and three secondary studies (Axelrod and Milner, 1997; Vasterling et al., 2003; White et al., 2001).

David et al. (2002) compared 209 UK veterans deployed to the Persian Gulf with 54 UK Bosnian peacekeepers and 78 nondeployed veterans. In this analysis no differences were found in neurobehavioral performance taking into account age, education, the National Adults Reading Test, and a depression score (Beck Depression Inventory). In the study of Proctor et al. (2003) the findings were verified with no differences found between 143 Danish Gulf War veterans and 72 non deployed veterans of the Danish military.

Of the secondary studies, only one (Axelrod and Milner, 1997) found differences between deployed and nondeployed veterans on the Stroop test of directed attention, following adjustment for age and education. White et al. (2001) combined two quite different samples (a cohort from Fort Devens and a second cohort from New Orleans) and compared this group to a small group of Germany-deployed veterans.

Studies in Symptomatic Veterans

In considering the neurobehavioral performance of symptomatic versus nonsymptomatic Gulf War veterans, two primary studies (David et al., 2002; Storzbach et al., 2001) and six secondary studies (Axelrod and Milner, 1997; Bunegin et al., 2001; Goldstein et al., 1996; Hom et al., 1997; Lange et al., 2001; Sillanpaa et al., 1997) were identified in Volume 4. Overall the definition of symptomatic was variable ranging from “any one of memory loss, confusion, mood

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