Objectives: This study aimed to compare brain magnetic resonance imaging (MRI) outcomes between children who play American football versus noncontact sport controls testing the hypotheses that history (primary) and duration (secondary) of football participation would be associated with differences in cortical thickness, subcortical volume, resting-state functional connectivity, and white matter diffusivity. Methods: This secondary analysis of cross-sectional baseline data from the Adolescent Brain Cognitive Development Study compared brain MRI outcomes between 9- and 10-year-old children who play American football (n = 1194) versus noncontact sport controls (n = 807). Outcomes included 74 bilateral cortical thickness regions; 10 gray matter subcortical volumes, with a priori focus on the hippocampi; resting-state functional connectivity (169 network-network correlations and 247 network-region correlations across 13 resting-state functional networks and 19 regions); and 21 diffusion tensor measures. Results: Football participation was associated with global effects on cortical thickness (P = 0.017), network-to-network resting-state connectivity (P = 0.010), and fiber tract volume (false-discovery rate [FDR]-adjusted P = 0.015) in primary analysis, but the only significant post hoc finding after FDR correction was smaller cortical thickness adjacent to the left anterior transverse collateral sulcus in the football group (Cohen d = -0.258, FDR-adjusted P = 0.017). There were no significant duration of football play effects in secondary analyses (all P > 0.05). Targeted analysis of hippocampal volumes yielded no significant football or duration of play results (both P > 0.05), but suggested a potential trend of lower hippocampal volumes with increasing duration of play. Conclusions: At ages 9-10, participation in American football was associated with minimal differences across a large array of structural, functional, and diffusion tensor MRI outcomes. While the clinical implications of these cross-sectional results are unknown, they merit additional investigation and can contribute to the ongoing discussion surrounding contact sport participation in children.
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