Improved frontoparietal white matter integrity in overweight children is associated with attendance at an after-school exercise program

Abstract

Aerobic fitness is associated with white matter integrity (WMI) in adults as measured by diffusion tensor imaging (DTI). This study examined the effect of an 8-month exercise intervention on WMI in children. Participants were 18 sedentary, overweight (BMI≥85th percentile) 8- to 11-year-old children (94% Black), randomly assigned to either an aerobic exercise (n=10) or sedentary attention control group (n=8). Each group was offered an instructor-led after-school program every school day for approximately 8 months. Before and after the program, all subjects participated in DTI scans. Tractography was conducted to isolate the superior longitudinal fasciculus and investigate whether the exercise intervention affected WMI in this region. There was no group by time interaction for WMI in the superior longitudinal fasciculus. There was a group by time by attendance interaction, however, such that higher attendance at the exercise intervention, but not the control intervention, was associated with increased WMI. Heart rate and the total dose of exercise correlated with WMI changes in the exercise group. In the overall sample, increased WMI was associated with improved scores on a measure of attention and improved teacher ratings of executive function. This study indicates that participating in an exercise intervention improves WMI in children as compared to a sedentary after-school program.

Figure 1

Time by group by attendance interactions. Y-axes show white matter difference scores (changes in integrity from baseline to post-test) and x-axes show attendance. Each measure shown is a residual (controlled for age and gender) which has been back-transformed to its original metric by adding its mean.

Figure 2

Illustrations of K-means cluster analyses. The scatterplots illustrate the two clusters identified for each analysis based on the participants' alterations in white matter integrity (FA and RD) over time. These show that for both analyses, Cluster 1 had improved white matter integrity (increased FA and decreased RD) compared to Cluster 2. The bar graphs illustrate the differences in cognition between the two clusters obtained in each analysis. In Cluster Analysis 1, Cluster 2 showed worse teacher ratings of executive function as compared to Cluster 1, indicated by increased BRIEF scores. In Cluster Analysis 2, Cluster 1 showed improved attention scores as compared to Cluster 2, indicated by increased CAS Attention Scale scores. The two clusters obtained in each k-means analysis significantly differed in all measures shown. SLF = superior longitudinal fasciculus. FA = fractional anisotropy. RD = radial diffusivity. BRIEF = Behavioral Rating Inventory of Executive Function. CAS = Cognitive Assessment System. Measures shown are difference scores (change from baseline to post-test).