Neurobehavioral test performance in the third National Health and Nutrition Examination Survey

Abstract

The third National Health and Nutrition Examination Survey (NHANES III) contained three computerized neurobehavioral tests from the Neurobehavioral Evaluation System (NES): simple reaction time, symbol–digit substitution and serial digit learning. The neurobehavioral data that were collected came from a nationally representative sample of adults 20–59 years old. Performance on the tests was related to sex, age, education level, family income and race-ethnicity. Performance decreased as age increased, and increased as education level and family income increased. Differences in performance between sexes, levels of education and racial-ethnic groups tended to decrease as family income increased. The relationship between age and performance on the symbol–digit substitution test varied by education level and by racial-ethnic group. The relationship between age and performance on the serial digit learning test varied by racial-ethnic group. Questionnaire variables that were related to performance on one or more of the tests included the reported amount of last night's sleep, energy level, computer or video game familiarity, alcoholic beverages within the last 3 h and effort. Persons who took the tests in English or Spanish performed differently on the symbol–digit substitution and serial digit learning tests. Performance on all the tests decreased as test room temperature increased.

Introduction

The National Center for Health Statistics periodically conducts large surveys to assess the health and nutrition of persons in the United States. The surveys consist of questionnaires, physical examinations and laboratory tests. The components of the surveys are administered in homes and in mobile examination centers. The surveys have provided national reference data for biological markers and anthropometric measurements (e.g., [20], [21], [32], [55], [61]). The last completed survey was the third National Health and Nutrition Examination Survey (NHANES III). This survey's documentation [49] and data [50], [51] are available on CD-ROM.

NHANES III contained three neurobehavioral tests from a computerized test battery called the Neurobehavioral Evaluation System (NES) that were used to assess central nervous system (CNS) function. The three tests were simple reaction time, symbol–digit substitution and serial digit learning. They are often referred to as the CNS component of the survey. The NES was designed to measure neurobehavioral performance in populations that are occupationally or environmentally exposed to chemicals [7], [8], [34], [35], [36], [38], [39]. It has been used to investigate the neurotoxic effects of organic solvents [6], [13], [15], [19], [24], [27], [48], organophosphate pesticides [47], [63], nitrous oxide [26], [46], styrene [40], [64], volatile organic compounds [53], lead [60], [65], [69], mercury [22], [23], [44], [65], tetrachloroethane [2] and sulfuryl fluoride and methyl bromide [16].

The purposes of this article are to describe the survey methods with respect to the neurobehavioral tests and to summarize the neurobehavioral data statistically using the demographic variables that were included in the survey and questionnaire items that were administered with the tests. There are no data for the NES from a large sample of the general population. The data collected by NHANES III are from a nationally representative sample. Estimates calculated from this sample can be used as reference values for workplace and other studies designed to explore the etiology of nervous system disorders. They provide a reference point against which future national surveys can be compared in order to evaluate trends over time. The estimates can be used for power and sample size calculations, and they can be used as a guide for deciding which variables to include and control for in future studies.