Changes in peripheral blood and cognitive performance after nonconcussive head impacts in elite female soccer players.

Background: Exposure to repetitive head impacts (RHI) has been shown to be associated with cognitive impairment and markers of neurodegeneration in professional male soccer players. However, data on the effects of RHI in female players are very limited. In this exploratory study, we investigated changes in blood biomarkers along with the cognitive status of elite female soccer players and compared the effect of RHI with outcomes in male players.

Methods: In a cohort study, elite female soccer players (age 16-41 years) performed training without heading the ball (n = 36) and training including heading (n = 30). Athletes were evaluated for the parameters of physical activity (heart rate) and neuropsychological testing (focused attention and cognitive flexibility) before and 1 h after each training. The levels of plasma tau, pTau₁₈₁, pTau₂₁₇ and microRNAs were determined at four timepoints: before training, 1 h, 24 h, and 48 h after each training session. Parameters in females were compared with control male players (n = 32).

Results: The levels of tau, pTau₁₈₁ and pTau₂₁₇ are significantly increased in the plasma of female soccer players 1 hour after physical exercise (tau, 1.4-fold; pTau₁₈₁, 1.3-fold; pTau₂₁₇, 1.2-fold) and repetitive head impacts (tau, 1.2-fold; pTau₁₈₁, 1.3-fold; pTau₂₁₇, 1.3-fold) compared to pre-training levels. The ratio of pTau₁₈₁ to tau fold change is significantly higher 1 hour after heading and remains elevated specifically in the heading group even after 48 h. The analysis of deregulated microRNAs in plasma reveals enrichment of neuroprotective pathways after heading training. Female soccer players show worse cognitive functions after heading compared to exercise and also compared to male soccer players.

Conclusions: RHIs may lead to acute disbalance of tau and phosphorylated tau in plasma, and are associated with short-term decline in cognitive performance and neuroprotective pathways in elite female soccer players. The sexual dimorphism in response to RHI may reflect biological risk factors potentially relevant to the different degree of susceptibility to neurological disorders in females and males in later life.