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A cohort study of neuropsychological change after a second season of head impact exposure in youth football

Arthur Maerlender[1]; Eric Smith2; P. Gunnar Brolinson[2],5; Jillian Urban[3]; Amaris Ajamil[4]; Steven Rowson2; Eamon T. Campolettano2; Ryan A. Gellner2; Emily Kieffer2; Mireille E. Kelley3; Derek Jones3; Alex Powers7; Jonathan Beckwith4; Joel Stitzel3; Stefan Duma2; Joseph Crisco6; Richard M. Greenwald4.


Importance: The accumulation of subconcussive head impact exposure is a concern for long term neurodegenerative disease. Further, the age of exposure is thought to raise risk levels. A recent study with a larger sample of first season youth football players identified an inverse relationship between neuropsychological score changes and the amount of head impact exposure. The follow-up second season data replicated and extended those findings. Objective. The objective of this study was to follow-up on the first season of participation to determine the nature, if any, of the neuropsychological effects of two seasons of head impact exposure. Design. This was two-tier cohort longitudinal study. Setting: Youth football players wore instrumented helmets at all practices and games in three eastern US states. Assessments were carried out in clinical settings, pre- and post-season. Participants: Sixty-eight youth football players who participatedin a second seasonof an NIH funded study of concussions in youth football were followed. The age range in season-2 was 10 to 13. All were male and 69% were Caucasian. Exposure(s): Head impact exposure was the primary independent variable. Participants wore helmets instrumented with Riddell Sideline Response System technology to measure accelerative forces. Main Outcome(s) and Measure(s): Following from the season-1 findings, the season-2 a priori hypotheses were that test scores adjusted for repeat testing would be lower at post season than pre-season, and that these changes would be inversely related to amount head impact exposure in the younger cohort. A battery of four neuropsychological tests were administered before and after each season. Following from the season-2 study, regression models were used to determine the effects of exposure and player weight on test score changes. Results: Twenty-seven participants from the original nine to 10-year old cohort and 41 from the original 11 to 13 group were followed. The hypotheses were confirmed: the list-learning test score changes again showed an inverse relationship to head impact exposure in the younger group, although with a smaller effect than in season-1: R2 = .124, F = 3.526, P = .036. Additional test scores were significantly related to HIE in both younger and older groups, with larger effect sizes. Conclusions and Relevance:  After two seasons of youth football, cognitive declines related to HIE were noted in the full sample, compared to declines in only the young group in season-1.  Although group-level clinical significance was not demonstrated, this analysis together with season-1, supports retrospective studies reflecting concerns about the safety of playing football under the age of 14.

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