This section focuses on neurobehavioral performance as measured by tests of cognition and in some cases sensory integrity or motor speed and coordination. For the purposes of this section, in addition to the criteria for primary and secondary studies established in Chapter 2, the committee required that primary studies of neurobehavioral effects have used data derived from neurobehavioral tests rather than relying on self-reports of neurobehavioral deficits. Secondary studies had additional methodologic limitations or did not include combat veterans (see Chapter 2). The secondary studies were reviewed and included in the discussion because they evaluated the same functional domains, such as attention and memory, and in some cases used the same neurobehavioral tests as did primary studies; they therefore provide valuable supplementary information that helps to increase or decrease confidence in the conclusions drawn from the primary studies. Confidence in a study is substantially reduced if its statistical analysis did not adjust for confounders or if individually administered neurobehavioral tests were given by examiners not blinded to the status of cases and controls; blinding is of less concern if tests were administered on a computer. Summaries of the primary studies are given in Table 6-5.
The committee identified three primary studies that compared deployed veterans with those deployed elsewhere or not deployed. David et al. (2002) compared the neurobehavioral-test performance of 209 UK soldiers deployed to the Persian Gulf, 54 UK Bosnia peacekeeping soldiers, and 78 UK Gulf War-era nondeployed soldiers. Study participants were a random sample of a larger cohort that had responded to an earlier mailed survey about symptoms, illnesses, and exposures (Unwin et al. 1999). A broad array of neurobehavioral tests were administered to all participants. The results of the data analysis were incompletely reported, so evaluation was limited by the lack of standard deviations of the mean test scores. No differences were reported among the groups after correction for age, education, intelligence (according to the National Adult Reading Test), and Beck Depression Inventory score.
Proctor et al. (2003) studied 143 Gulf War veterans and 72 nondeployed veterans of the Danish military; participants were randomly selected from among the 916 Gulf War deployed veterans and 236 nondeployed veterans studied by Ishoy et al. (1999). Deployed veterans served in the gulf region during August 1990-December 1997 as peacekeepers and thus had no direct combat exposure. Neuropsychologic tests addressing mood, attention, executive function, motor skills, visuospatial abilities, verbal memory, and visual memory were administered. The self-reports of Danish Gulf War veterans suggested a significantly higher prevalence of eight of 16 neuropsychologic symptoms than their nondeployed counterparts, but no significant differences between the deployed and the nondeployed were found by thorough analyses of the data from the neurobehavioral tests.
In the Neurocognition Deployment Health Study, Vasterling et al. (2006) determined the effects of war-zone deployment on neuropsychologic health. A cohort of 654 active-duty Army soldiers were examined before deployment to Iraq in 2003 as part of OIF and on return from Iraq deployment in 2005 and were compared with 307 soldiers who were similar in military characteristics but not deployed overseas. After adjustment for deployment-related head injury, stress, and depression, deployment to Iraq was associated with statistically significant