Acute Subconcussive Effect on Plasma Neurofilament Light Polypeptide in Collegiate Soccer Players

Abstract

Research continues to allude to the efficacy of using blood biomarkers as tools to detect brain parenchymal damage in the periphery of the body. While emerging evidence supports the use of neurofilament light polypeptide (NF-L) as a specific blood biomarker of cerebral trauma, the cogency of its use with respect to repetitive subconcussive head impacts remains elusive. Therefore, the purpose of this study was to investigate the acute effects of subconcussive head impacts on plasma NF-L levels in the collegiate soccer cohort. To be considered for inclusion, participants were required to have at least three years of soccer heading experience and be between the ages of 18 and 26. Conversely, participants were excluded if they had a history of head injury during one year prior to the study or a history of neurological disorders.

In effort to test our central hypothesis that plasma levels of NF-L will increase in proportion to the amount of subconcussive head impact experienced, thirty-four participants were distributed between kicking-control and heading groups and assessed at four time points (pre-intervention, 0h-post, 2h-post, and 24h-post intervention). At each time point, a blood sample was collected from each participant. Between the pre- intervention and the 0h-post time point, each participant completed an intervention based on random group assignment. Participants in the heading group performed 10 soccer headers, while the kicking-control group performed 10 kicks. The ball was released by a JUGS machine approximately 40 feet from the participant at a speed of 25mph, inducing an average force of about 30g, similar to that of a long-throw during a soccer game, in one-minute intervals.

Our results support previous findings that NF-L expression markedly increases in proportion to subconcussive head impacts cumulatively, with a significant increase at 24h post-heading. Subconcussive head impacts gradually increased plasma NF-L expression, as illustrated by a significant time by group interaction, F(1, 31) = 9.17, p = 0.0049, while the kicking-control group remain consistent throughout the study time points. A significant difference was revealed at 24h post-heading (3.68 $\pm$ 0.30 pg/mL) compared to pre-heading (3.12 $\pm$ 0.29 pg/mL, p = 0.0013; Cohen’s d = 1.898). The heading group (3.68 $\pm$ 0.30 pg/mL) showed a significantly higher level of plasma NF-L than the kicking-control group (2.97 $\pm$ 0.24 pg/mL: p = 0.038: Fig 1). There are two chief findings from this study: 1) There was no significant increase in NF-L expression until the 24h post-heading assessment in the heading group and 2) NF-L expression remained consistent across all time points in the kicking-control group. These findings suggest potential for cumulative effects of subconcussive head impacts.

As research continues to reflect the negative neurocognitive effects of subconcussive head impacts, it is imperative that a gold standard for determining diagnosis, treatment, and prognosis is established. Our study further supports the efficacy of using biomarkers, specifically NF-L, in the triage and management of brain injuries.