Physical fitness, hippocampal functional connectivity and academic performance in children with overweight/obesity: The ActiveBrains project

Objectives: Physical fitness is a modifiable factor associated with enhanced brain health during childhood. To our knowledge, the present study is the first to examine: (i) whether physical fitness components (i.e., cardiorespiratory, motor and muscular fitness) are associated with resting state functional connectivity of hippocampal seeds to different cortical regions in children with overweight/obesity, and (ii) whether resting state hippocampal functional connectivity is coupled with better academic performance. Patients and methods: In this cross-sectional study, a total of 99 children with overweight/obesity aged 8-11 years were recruited from Granada, Spain (November 2014 to February 2016). The physical fitness components were assessed following the ALPHA health-related fitness test battery. T1-weighted and resting-state fMRI images were acquired with a 3.0 Tesla Siemens Magnetom Tim Trio system. Academic performance was assessed by the Woodcock-Munoz standardized test. Hippocampal seed-based procedures with post-hoc regression analyses were performed. Results: In the fully adjusted models, cardiorespiratory fitness was independently associated with greater hippocampal connectivity between anterior hippocampus and frontal regions (beta ranging from 0.423 to 0.424, p < 0.001). Motor fitness was independently associated with diminished hippocampal connectivity between posterior hippocampus and frontal regions (beta ranging from -0.583 to -0.694, p < 0.001). However, muscular fitness was not independently associated with hippocampal functional connectivity. Positive resting state hippocampal functional connectivity was related to better written expression (beta ranging from 0.209 to 0.245; p < 0.05). Conclusions: Physical fitness components may associate with functional connectivity between hippocampal subregions and frontal regions, independent of hippocampal volume, in children with overweight/obesity. Particularly, cardiorespiratory fitness may enhance anterior hippocampal functional connectivity and motor fitness may diminish posterior hippocampal functional connectivity. In addition, resting state hippocampal functional connectivity may relate to better written expression.