NES test performance in a large US Army veteran sample: relationships with both demographic factors and traditional neuropsychological measures.

A large sample of Vietnam-era US Army veterans completed a set of 16 neuropsychological tests, including six computer-based tests from the Neurobehavioral Evaluation System (NES), during medical examinations supervised by the US Centers for Disease Control (CDC). Data for 881 participants of the Agent Orange Validation Study (AOV) and Vietnam Experience Study (VES) were available for analysis from public access data tapes provided by CDC. Information was available for several potential covariates from demographic questionnaires, a medical examination, and a medical history. Explorator, principal components factor analysis of 16 test variables yielded four factors, including one on which most of the NES tests loaded. The single best predictor of most neuropsychological performance variables was an index of general intellectual level as measured at entry into the Army almost 20 years before the neuropsychological examinations. Alcohol drinking variables were not related to neuropsychological performance. Several measures of general intelligence were compared for use as covariates of neuropsychological test performance. All were superior to years of education in statistically controlling for general intellectual level.