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Objective: Youth athletes are believed to be more susceptible to white matter (WM) degradation resulting from head impact exposure relative to high school (HS) athletes; this hypothesis has not been objectively tested. The purpose of this study was to determine preseason to postseason changes in WM integrity from repetitive head impacts for youth football (YFB) players compared with HS football players during a competitive football season.

Design: Prospective cohort.

Setting: One season of YFB (grades 7 and 8) and varsity HS football (grades 10-12).

Patients or Other Participants: Twelve YFB (13.08 /- 0.64 years) and 21 HS (17.5 /- 0.78 years) athletes.

Interventions: Participants completed 2 magnetic resonance imaging sessions: preseason and postseason. Head impact exposure was recorded during practice and games using a helmet-mounted accelerometer.

Main Outcome Measures: Tract-based spatial statistics were used to evaluate group differences in preseason to postseason changes in diffusion tensor imaging, including fractional anisotropy and mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD).

Results: The HS group exhibited significant preseason to postseason reductions in MD, AD, and RD (P < 0.05, corrected) in widespread WM areas. Significant WM reductions for the YFB group were only observed for AD (P < 0.05, corrected), but was more limited in extent compared with HS.

Conclusions: Significant preseason to postseason AD reduction was found in both YFB and HS groups after one season of competitive play. Our results did not confirm recent speculation that younger children are more susceptible to the deleterious effects of repetitive head impacts compared with their older counterparts.

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