Neurodevelopmental profiles of 4-year-olds in the Navajo Birth Cohort Study

Abstract

Objective: Native American children disproportionally face many risk factors for poor developmental outcomes; these factors include poverty, environmental toxicant exposure, and limited medical, and intervention services. To understand these risks, comprehensive documentation of developmental and behavioral phenotypes are needed. In the current descriptive study, we assessed the neurodevelopment of young Diné (Navajo) children using standardized assessment instruments in combination with expert clinician judgment.

Methods: As part of an ongoing, population-based, prospective birth cohort study, we conducted comprehensive neurodevelopmental assessments of 138, 3-5-year-old, Diné children residing on or near the Navajo Nation. We report results from standardized parent reports, psychiatric examinations, and direct assessments of children's language, cognitive, adaptive, and social-emotional development, as well as best estimate clinical diagnoses.

Results: Forty-nine percent of our sample met DSM-5 criteria for a neurodevelopmental disorder (NDD) diagnosis. Language and speech sound disorders were most common, although autism spectrum disorder (ASD) was also elevated compared to the general population. Though language performance was depressed amongst all groups of children with, and without, NDDs, those meeting criteria for certain NDDs performed significantly lower on all language measures, when compared to those without. Social-emotional, behavioral, and nonverbal cognitive ability were in the average range overall.

Conclusions: Diné children in our study were found to have a high percentage of clinically significant developmental delays. Overall, children presented with a pervasive pattern of depressed language performance across measures, irrespective of diagnosis (or no diagnosis), while other domains of functioning were similar to normative samples. Findings support the need to identify appropriate intervention and educational efforts for affected youth, while also exploring the causes of the specific developmental delays. However, longitudinal studies are necessary to establish best practices for identifying delays and delineating resilience factors to optimize development of Diné children.

Keywords: American Indian; Native American; indigenous; language; neurodevelopment.

Figure 1

Line Plot of Mean Standardized Scores on Main Abilities Measures Across Groups (Higher Scores Better Functioning) Note:Standardized scores across diagnostic groups on ability measures of DAS, OWLS and Vineland. ABC =Adaptive Behavior Composite; ASD = autism spectrum disorder; DAS = Differential Ability Scales; GCA = General Conceptual Ability; ID/GDD = intellectual disabilities or global developmental delays; NDD = neurodevelopmental disorder; NVR = Nonverbal Reasoning; OWLS = Oral and Written Language Scales; SNC = Special Nonverbal Composite; VABS = Vineland Adaptive Behavior Scales.

Figure 2

Line Plot of Standardized Scores on Main Impairments Measures Across Groups (Higher Scores More Impairments) Note:Reference case (red, square markers) was with T scores of 50 before conversion to z scores. ASD = autism spectrum disorder;CBCL = Child Behavior Checklist; ID/GDD = intellectual disabilities or global developmental delays; NDD = neurodevelopmental disorder; RRB = Restricted Interests and Repetitive Behavior; SCI = Social Communication and Interaction; SRS = Social Responsiveness Scale.