1. Even among single-born children not diagnosed with developmental disabilities, later achievement of some infant motor milestones was associated with worse performance on tests of developmental skill.
2. In contrast to singletons, after adjusting for gestational age and birth weight, none of the gross motor milestones considered were significantly associated with total developmental score in twins.
Study Rundown: The basal ganglia, a group of nuclei responsible for motor regulation, are also known to influence cognitive function. This connection provides a possible explanation for why children with developmental differences are thought to meet motor milestones at later times than their typically developing peers. Prior to this study, it was unknown whether such milestones could also serve as predictors of cognitive function among children with typical cognitive abilities. By analyzing maternally reported data on motor milestones from the Upstate KIDS study and performing cognitive function testing on a subset of participants at age 4, researchers were able to investigate their hypothesis that both single-born children and twins with later motor development would have worse performance on cognitive function tests. Singleton data was consistent with this hypothesis—not only was later achievement of motor milestones such as standing with assistance predictive of lower total Battelle Developmental Inventory, Second Edition (BDI-2) score in the entire cohort (most notably for adaptive and cognitive skills) but also time of hands-and-knees crawling was associated with total BDI-2 score among children without developmental disabilities. Although possibly underpowered, twin data argued against a predictive role in this subpopulation. Additional limitations of this study were the potential for bias introduced by the restricted sample of the original cohort, lack of follow-up into adulthood, and the performance of multiple comparisons, diminishing statistical significance. Nevertheless, results highlight the potential utility of infant motor milestones as predictors of cognitive function and suggest the clinical relevance of monitoring such progression.
Relevant Reading: Cognitive-motor interactions of the basal ganglia in development
In-Depth [longitudinal study]: Participants included a subsample of the Upstate KIDS study (599 of 6171 children), a population-based birth cohort selected to study the effects of infertility treatment on child development. Such children were born between 2008 and 2010 in Upstate New York and met inclusion criteria such as failing a developmental screening questionnaire (or being randomly selected despite passing) or simply being a non-singleton baby. Gross motor development was maternally reported at 4-month intervals from 4 months to 1 year and also at 1.5 and 2 years. Sitting without support, standing with assistance, hands-and-knees crawling, walking with assistance, standing alone, and walking alone were recorded. At 4 years of age, the BDI-2 was administered to determine a total developmental score in addition to specific scores for personal/social, adaptive, motor, communication, and cognitive development. After adjusting for developmental disabilities and infertility treatment exposure, later achievement of standing with assistance was the only milestone that remained associated with a lower total developmental score (multivariate linear regression slope B = -21.9, 95%CI: -41.5 to -2.2, p = 0.03). More specifically, time of achieving this milestone had the greatest association with adaptive (B = -5.3, 95%CI: -9.0 to -1.6, p = 0.01) and cognitive (B = -5.9, 95%CI: -11.5 to -0.4, p = 0.04) BDI-2 scores. Even among children without developmental disabilities, later hands-and-knees crawling was associated (p < 0.05) with lower total developmental score (B = -23.4, 95%CI: -42.9 to -3.9). In twins, none of the motor milestones remained significantly associated with total BDI-2 score after adjusting for gestational age and birth weight.
©2015 2 Minute Medicine, Inc. All rights reserved. No works may be reproduced without expressed written consent from 2 Minute Medicine, Inc. Inquire about licensing here. No article should be construed as medical advice and is not intended as such by the authors or by 2 Minute Medicine, Inc.