Interpreting Patterns of Low Scores on the NIH Toolbox Cognition Battery

Introduction: The National Institutes of Health Toolbox for Assessment of Neurological and Behavioral Function Cognition Battery is comprised of seven cognitive tests, including two tests measuring crystallized cognitive ability (i.e., vocabulary and reading) and five tests measuring fluid cognitive functioning (i.e., working memory, memory, speed of processing, and executive functioning). This study presents comprehensive base rate tables for the frequency of low scores in adults and older adults from the normative sample. Methods: Participants were 843 adults, ages 20-85, from the NIH Toolbox standardization sample who completed all seven cognition tests. Rates of low scores were derived for standard age-adjusted and fully-demographically-adjusted scores at multiple cut-scores. Base rates were stratified by education, crystallized intellectual ability, and cognitive domain. Results: Using the five demographically-adjusted fluid cognitive test scores, 45.9% of adults obtained one or more scores at or below the 16th percentile, and 16.8% obtained one or more score at or below the 5th percentile, which is consistent with findings from other neurocognitive test batteries. Discussion: Based on the study findings, nearly 50% of adults in the general population would meet psychometric criteria for a diagnosis of the Diagnostic and Statistical Manual of Mental Disorders-Fifth Edition (DSM-5) Mild Neurocognitive Disorder (MND). We developed new psychometric criteria for identifying MND using the NIH Toolbox Cognition Battery that reduce the false positive rate. Knowing these multivariate normative base rates will help researchers and clinicians interpret NIH Toolbox scores in people with neurodevelopmental, psychiatric, medical, neurological, and neurodegenerative disorders that affect cognitive functioning.