Head Trauma Biomarkers In NCAA Men’s Soccer Athletes Over The Course Of A Season

Abstract

Repetitive subconcussive impacts to the head are commonplace in soccer. The ability to detect the extent of neurological injury due to these impacts over the course of a season is paramount. PURPOSE: The purpose of the current study was to examine alterations in blood biomarkers of head injury over the course of a soccer season. METHODS: Sixteen National Collegiate Athletic Association (NCAA) male soccer athletes (20.1±1.3 years, 178.6±8.3 cm, 77.8±11.3 kg, 15.0±6.0 %BF) participated in weekly blood sampling throughout an 18-week season. Coaches provided player statistics following the season. Headers (HEAD) were defined as any impact of the players’ head with the ball. Serum samples were stored at -80°C until analysis for Tau and Neurofilament Light polypeptide (NFL). We used R statistical language and the lme4 statistical package to perform a linear mixed effects analysis of the relationships of minutes played (MP) and HEAD with Tau and NFL. We included the intercept for subjects as a random effect, and time point (TP), MP, and HEAD (without the interaction term) as fixed effects. P-values for model comparisons were obtained by likelihood ratio tests of the full model with the effect in question against the model without the effect in question. Visual inspection of residual plots did not reveal any obvious heteroscedasticty or deviation from normality. RESULTS: NFL was significantly elevated in weeks 5 (7.3±2.8pg/mL; p<0.001), 14 (7.0±3.1pg/mL; p=0.047), and 15 (7.9±4.0pg/mL; p<0.001) compared to baseline (5.2±1.2 pg/mL). Tau did not change significantly over the course of the season. Neither adding MP (χ2(1)=1.85, p=0.17, ΔAIC=0.2) nor adding HEAD (χ2(1)=0.15, p=0.69, ΔAIC=1.85) as fixed effects improved the model fit for Tau, compared to the simpler model with TP. Similarly, the addition of MP did not improve model fit for NFL (χ2(1)=1.50, p=0.22, ΔAIC=0.5). Conversely, including HEAD improved the model for NFL compared to the simpler model with TP (χ2(1)=5.68, p=0.02, ΔAIC=-3.7). However, only a small negative effect of HEAD, -0.09 (95%CI=-0.16, -0.02), was detected. CONCLUSION: In our study, neither MP nor HEAD had a significant effect on Tau concentration over the course of an NCAA Men’s soccer season. HEAD appeared to have a small negative effect on NFL concentrations across the season.