Reduced cortical thickness in the prefrontal cortex (PFC) related to childhood obesity may result in compromised executive function, according to study results published in Cerebral Cortex.
Maturation of the PFC is linked to the development of executive function in childhood and pediatric obesity has been associated with changes in the PFC. To assess whether these changes mediate the relationship between increased adiposity and executive functioning, investigators analyzed magnetic resonance-derived measures of cortical thickness and related them to body mass index (BMI) and executive function scores of 2700 children between the ages of 9 and 11 years.
Children were part of the National Institutes of Health Adolescent Brain and Cognitive Development (ABCD) study, which included a battery of executive functioning and imaging tests. Obesity was assessed using BMI and BMI z scores based on sex and age. Because puberty affects cortical thickness development, investigators also included dehydroepiandrosterone (DHEA) level as a covariate, as well as age, sex, race, birth weight, and in-scanner motion, among other factors.
Boys tended to be heavier than girls based on BMI z scores (β =0.1, t =2.4; P =.02), while girls had slightly higher executive functioning (β =0.1, t =2.4; P =.02). Increased BMI was associated with significantly reduced mean global cortical thickness (P =.01) and specific bilateral reduced cortical thickness in prefrontal regions. Increased BMI was also associated with lower executive functioning (P =.02). In turn, the reductions in executive function were significantly related to mean global cortical thickness; this relationship was at least partially explained by reduced thickness in the inferior frontal gyrus, the rostral medial and superior frontal cortex, and the lateral orbitofrontal cortex.
On a covariate level, BMI z score was positively associated with salivary DHEA levels (β =0.17; t =6; P <.001), suggesting that increased BMI was linked to more advanced pubertal stages. Investigators also found a positive association between levels of DHEA and executive abilities (β =0.09; t =2.9; P =.005). Such variables as birth weight, race, and in-scanner motion were associated with both BMI z score and executive function, whereas age was only associated with executive abilities (β =0.09, t =4.5; P <.001).
Overall, the investigators concluded that the association between increased BMI and lower executive function in childhood is likely mediated by their shared relationship with thickness of PFC regions. However, they were unable to distinguish between different possible models to determine the causal relationship between BMI, executive function, and cortical thickness due to the cross-sectional nature of the available data.
In addition, BMI is less directly related to cardiometabolic risks than metrics such as waist circumference and waist-to-height ratio and may not fully capture the variations in cortical thickness as they relate to adiposity.
“The data are consistent with a mechanism whereby PFC changes in childhood obesity may lead to altered regulation of inhibitory control and risk-taking behavior and further difficulties in weight control,” the investigators wrote.
Disclosure: One study author declared previous affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.
Ronan L, Alexander-Bloch A, Fletcher PC. Childhood obesity, cortical structure, and executive function in healthy children [published online October 24, 2019]. Cereb Cortex. doi:10.1093/cercor/bhz257