title: Human neurobehavioral research methods: impact of subject variables.
abstract: Behavioral tests are used in work site and community research to detect and characterize the effects of neurotoxic chemical exposures in human populations, but the influence of subject variables on test performance has not been well studied in normal adult populations. This research sought to evaluate the impact of two variables, education and cultural group, on 18 widely used tests of neurotoxic insult. Behavioral tests from the two consensus neurotoxicity test batteries (established by the World Health Organization and the U.S. Agency for Toxic Substances and Disease Registry) were administered to 715 people aged 26-45 with 0-18 years of education, drawn from European descent United States majority, American Indian, African American, and Latin American populations. Education, cultural group, age, and gender affected the outcome of behavioral tests as revealed by ANOVA, MANOVA, and multiple regression techniques. Education, followed by cultural group, accounted for the most variance in the tests studied. More importantly, years of education and cultural group had 13-25% shared variance on the cognitive tests and highly significant interactions derived from ANOVA tests. This suggests that these factors should be controlled in the design of a study rather than in the statistical analysis. Because these factors can mimic a neurotoxic insult, failure to adequately control and analyze them could lead to inaccurate conclusions about the association between poor performance and neurotoxic insult.
authors.affiliation: Center for Research on Occupational and Environmental Toxicology, Oregon Health Sciences University, Portland, Oregon 97201, USA.
authors.forename: W K
authors.initials: WK
authors.lastname: Anger
authors.forename: O J
authors.initials: OJ
authors.lastname: Sizemore
authors.forename: S J
authors.initials: SJ
authors.lastname: Grossmann
authors.forename: J A
authors.initials: JA
authors.lastname: Glasser
authors.forename: R
authors.initials: R
authors.lastname: Letz
authors.forename: R
authors.initials: R
authors.lastname: Bowler
mesh_terms: D000328:Adult; D000367:Age Factors; D001519:Behavior / Q000187:drug effects*; D003466:Cultural Characteristics; D004522:Educational Status; D004785:Environmental Pollutants / Q000506:poisoning*; D005006:Ethnicity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009420:Nervous System / Q000187:drug effects* / Q000503:physiopathology; D009483:Neuropsychological Tests; D015203:Reproducibility of Results
chemical_list: D004785:Environmental Pollutants