Longitudinal assessment of brain injury biomarker neurofilament light in female football players during a competitive season of football heading

This prospective cohort study aimed to longitudinally assess the brain injury biomarker plasma neurofilament light (NfL) and its relationship with football heading exposure in female football players during a competitive season. Forty-nine collegiate female football players were recruited to participate in the study, 29 voluntarily consented and enrolled. Blood samples were collected every 3-4 weeks during season: preseason, midseason 1, 2, and postseason. Heading exposure was estimated every two weeks via HeadCount questionnaire. Linear mixed models for repeated measures were used to determine differences in plasma NfL during the season. Spearman's rank correlation analysis determined the relationship between NfL changes and heading exposure. For analysis, participants were excluded if unable to participate in ≥ 80% of team activities or experienced a concussion during the season; thus, six were excluded resulting in 23 participants' data analyzed. NfL at mid- and postseason did not differ from preseason (mid1: p = 0.57; mid2: p = 0.88; postseason: p = 0.07). Changes in NfL from preseason were unrelated to gameplay heading exposure at any time points and cumulative exposure at midseason 1, 2. Changes in NfL and cumulative heading exposure from pre- to postseason were positively correlated (r = 0.434, p = 0.039), with lower exposures associated with reductions in NfL and higher exposures showing minimal to no elevations. In conclusion, plasma NfL did not elevate in collegiate female football players during a competitive season of heading exposure. However, whether these findings reflect no subtle brain injury or NfL's insensitivity in detecting said injury in young female players remains unclear.