Neurofilament light and tau in serum after head-impact exposure in soccer

ABSTRACT

Introduction: Blood-based biomarkers can provide valuable information on the effects of repetitive head impacts in sports. This study investigated if repetitive headers or accidental head impacts in soccer could cause structural brain injury, detected as an increase in serum neurofilament light (NfL) or tau.

Methods: NfL and tau were measured in professional soccer players in pre-season. Then, the effect of three short-term exposures on biomarker levels was assessed: (1) high-intensity exercise, (2) repetitive headers, and (3) head impacts in a match.

Results: We analyzed 354 samples and observed no effects on NfL from any of the three short-term exposures. Tau levels rose significantly from baseline to 1 h after (1) high-intensity exercise (Δ0.50 pg/mL, 95% CI 0.19–0.81, p < .01); the same was observed after (2) repetitive headers (Δ0.29 pg/mL, 95% CI 0.10–0.48, p < .01), but not after (3) accidental head-impact incidents (Δ0.36 pg/mL, 95% CI −0.02–0.74, p = .06). The highest absolute values were seen 1 h after high-intensity exercise (mean±SD, 1.92 ± 0.83 pg/mL).

Conclusion: NfL and tau in serum were unaffected by head impacts in soccer. Importantly, tau levels seem to rise in response to exercise, emphasizing the need for control groups. Our findings highlight important characteristics and limitations when using these biomarkers in sports.

KEYWORDS:

• Subconcussive
• TBI
• chronic traumatic encephalopathy
• football
• repetitive head impacts

Acknowledgments

The authors are grateful to all the players, medical staff and research personnel who took part in the original study. We thank Jiri Dvorak and Marianne Jochum for their contributions in the original study design and analyses. For their outstanding help in data collection and blood sampling, we also thank Jostein Steene-Johannesen, Grete Steene-Johannesen, Hilde Mikkelsen Bakka, John Bjørneboe and Torbjørn Soligard.

Disclosure statement

This work was part of the study RepImpact, and was funded by ERA-NET NEURON and The Research Council of Norway. The original study was funded by the International Federation of Association Football Medical Assessment and Research Center. The Oslo Sports Trauma Research Center has been established at the Norwegian School of Sport Sciences through generous grants from the Royal Norwegian Ministry of Culture, the South-Eastern Norway Regional Health Authority the International Olympic Committee, the Norwegian Olympic Committee and Confederation of Sport, and Norsk Tipping AS. No other competing financial interests exist.

Additional information

Funding

This work was supported by the The Research Council of Norway, ERA-NET Neuron.