Beyond Stature – Unraveling the Link between Early Life Growth and Cognition in a Well-Nourished US Cohort

Yi Ying Ong, PhD ​

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​Have you ever wondered, is faster growth in early life linked to faster brain development and smarter children? Undoubtedly, the brain undergoes remarkable growth during both fetal development and the early years of life, playing a role in the establishment of diverse cognitive processes. Poor fetal growth, stunting (too short), or wasting (too thin) have been consistently linked to poorer cognition. Healthy growth in early life is therefore important for brain growth and development. But is faster growth better in general? Conflicting findings from limited studies in high-income countries raise questions about whether we have reached the limits of biological intelligence that better growth can confer, and whether there are any negative impacts of excessive growth at specific early life periods on cognition. Our study aimed to address these questions.

We conducted our study in Project Viva, a large prospective cohort in the United States. We modeled height and BMI growth trajectories for 1,052 children and obtained their standardized growth rates in early infancy (0-4 months), late infancy (4-15 months), toddlerhood (15-37 months), and early childhood (37-84 months). We investigated the associations between growth rates and mid-childhood cognition – intelligence quotient (IQ), visual memory and learning, and visual motor ability. We adjusted for a comprehensive list of potential confounders including both parents’ education, height, child’s gestational age, size at birth, growth at preceding age periods, and other prenatal and sociodemographic confounders. Furthermore, we investigated if the association between postnatal growth and child cognition differed between children who had vs. had not experienced poor fetal growth (born small-for-gestational age).
 
We found that faster linear growth at any period from age 0-7 years did not provide consistent cognitive gains or deficits in mid-childhood. Our finding is consistent with previous studies in Project Viva and the Avon Longitudinal Study on Parents and Children (ALSPAC) which both found no associations between infant weight or length gain and child cognition. Unlike studies in low- and middle-income countries which found consistent associations between linear growth and cognition, there is almost no stunting/wasting occurring in our cohort, and most children were able to reach their growth potential.
While this overall finding suggested no overall relationship, we wanted to examine other outcomes and subgroups. And some associations emerged. We found that faster linear growth in early infancy (0-4 months) was significantly associated with higher visual motor ability (ability to copy/draw designs arranged in order of increasing difficulty). This is consistent with a prior study which found that better visual-motor integration seemed to be predominantly predicted by faster growth in infancy from 0-5 months. The importance of the early infancy period on visual motor skills might be linked to a rapid burst of synapse formation in the primary visual cortex between 2 to 4 months of age, with the primary visual cortex attaining adult size at around 4 months of age.
Additionally, we found that faster BMI gain, particularly at late infancy, was associated with slightly lower verbal IQ and design memory (draw geometric designs from memory) in mid-childhood. This finding is consistent with prior studies in the US which investigated weight-for-height or fat mass gain on child cognition. While the effect sizes are small, which might not warrant serious concern at this stage, the increasing prevalence of child obesity (nearly 20%) in the US might have small but significant influences on some types of cognition at a population-level. 

Finally, we found that faster linear growth, specifically in early infancy, was associated with higher non-verbal IQ among children who were small-for-gestational age. Our finding reveals the potential importance of early infancy compensatory (i.e., “catching up”) linear growth in this vulnerable group. Given that poor fetal growth occurs in nearly 10% of pregnancies in the US, our study highlights the need to consider both prenatal and postnatal growth trajectories in clinical practice.
Overall, these findings suggest some subtle connections between growth and some aspects of cognition for certain children. Vigilance to childhood growth, especially among those children gaining weight too quick or who were small-for-gestational age at birth, is critical to ensuring that children have healthy development. 

About the Author:

​Dr. Yi Ying Ong, PhD is a Research Fellow at the Harvard T.H. Chan School of Public Health. She received her undergraduate degree in Biomedical Sciences, and graduate degree in Epidemiology from the National University of Singapore. Her postdoctoral research focuses on the early life determinants of cognition, behavior, and puberty. In her free time, Yi Ying enjoys practicing yoga and playing tennis.