Season-long head acceleration exposure, prior contact-sport history, and cognitive performance in British amateur American football players

Background: Head acceleration events (HAEs) are common in contact sports, but season-long exposure and its relationship with cognitive performance in amateur British American football remain poorly characterised. Methods: Thirty male players were recruited from three British amateur American football teams. Selected Sport Concussion Assessment Tool 6 (SCAT6) components and computerised tasks were assessed across the season. Seasonal analyses included 20 participants, and exposure-linked analyses included 17. Helmet-sensor events were attributed to participants and restricted to participant-assignment and baseline-to-post-season calendar windows. Mixed-effects models assessed seasonal outcomes. Principal component analysis (PCA) summarised standardised baseline-to-post-season changes, and six exposure associations were evaluated. Results: Players recorded a mean of 768 (SD 482) events. Several individual tests improved across the season. The first principal component (PC1) explained 21.9% of change variance and had loadings with opposing signs. Prior seasons had a nominal association with PC1 (slope -0.153, 95% CI -0.305 to -0.00018; r2=0.233; p=0.0498), which did not survive six-test Benjamini-Hochberg (BH) adjustment (p=0.299). No in-season exposure association survived adjustment. Conclusion: Repeated-test performance improved, while exposure associations remained uncertain. The mixed PC1 pattern cannot be interpreted as a uniform measure of global cognitive worsening or improvement.