Serum Neurofilament Light in American Football Athletes over the Course of a Season.

Despite being underreported, American football boasts the highest incidence of concussion among all team sports, likely due to exposure to head impacts that vary in number and magnitude over the season. This study compared a biological marker of head trauma in American football athletes with non-contact sport athletes and examined changes over the course of a season. Baseline serum neurofilament light polypeptide (NFL) was measured after 9 weeks of no contact and compared with a non-contact sport. Serum NFL was then measured over the course of the entire season at eight time-points coincident with expected changes in likelihood of increased head impacts. Data were compared between starters (n = 11) and non-starters (n = 9). Compared with non-starters (mean ± standard deviation) (7.30 ± 3.57 pg•mL-1) and controls (6.75 ± 1.68 pg•mL-1), serum NFL in starters (8.45 ± 5.90 pg•mL-1) was higher at baseline (mean difference; ±90% confidence interval) (1.69;  ± 1.96 pg•mL-1 and 1.15;  ± 1.4 pg•mL-1, respectively). Over the course of the season, an increase (effect size [ES] = 1.8; p < 0.001) was observed post-camp relative to baseline (1.52 ± 1.18 pg•mL-1), which remained elevated until conference play, when a second increase was observed (ES = 2.6; p = 0.008) over baseline (4.82 ± 2.64 pg•mL-1). A lack of change in non-starters resulted in substantial differences between starters and non-starters over the course of the season. These data suggest that a season of collegiate American football is associated with elevations in serum NFL, which is indicative of axonal injury, as a result of head impacts.