Season-long studies of teenage soccer players provide reassurance about short-term brain health, but elevated preseason biomarkers show why the heading debate is far from settled.
Research: Youth soccer participation and its impact on brain health in youth athletes. Image credit: Master1305 / Shutterstock
In a recent study published in JAMA network openresearchers conducted a longitudinal study to determine how competitive youth soccer, specifically heading the soccer ball, is associated with brain health outcomes in the developing brain. The study followed 129 male athletes over one season and assessed the participants’ cognitive performance, behavior, balance, and neuroimaging metrics.
Encouragingly, the study results did not detect any short-term, group-level, statistically significant changes in brain structure, function, or cognitive health compared to non-contact sports athletes. These findings indicate that one season of competitive youth soccer is not associated with detectable deleterious changes in the measured neurological domains. However, clear preseason differences in neurological biomarkers between soccer players and controls indicate the need for extended follow-up over multiple years.
background
Soccer has long been considered the most popular sport in the world. Current estimates highlight that more than 22 million young people worldwide participate in some form of soccer, either competitively or recreationally. But “heading,” the unique act of hitting the ball with the head, is increasingly fueling medical debate over athlete safety.
Researchers and clinicians have expressed concern that repeated head impacts (RHI), subconcussive blows that do not cause a full concussion, may jeopardize the rapid brain maturation of adolescents. These concerns are based in part on data from retired professional athletes, which previously linked long-term exposure to “heading” to an increased risk of neurodegenerative diseases later in life.
Unfortunately, scientific evidence regarding immediate and short-term effects on adolescents remains lacking, limiting interpretation for young competitive soccer players. This uncertainty has caused parental anxiety and has led to precautionary heading restrictions in several countries.
About research
The current ‘REPIMPACT’ study aimed to address this knowledge gap and inform future sports medicine by systematically assessing whether a single competitive soccer season produces changes in neurological health in adolescents.
The REPIMPACT study is a longitudinal, prospective, multicenter cohort study conducted at three European sites: 1. Munich, Germany; 2. Leuven, Belgium; and 3. Oslo, Norway. The study sample cohort consisted of 129 male athletes aged 14 to 16 years, including 82 academy-level soccer players who practiced at least three times per week and 47 age-matched controls who participated in non-contact sports such as swimming, track and field, cycling, and racquet sports.
It is noteworthy that this study excluded participants with a history of physician-diagnosed concussions, thereby reducing the confounding effect of head trauma on daily playing outcomes. Research data were collected in three different stages. 1. Preseason, 2. Postseason, 3. Two months after the season under investigation.
The study specifically analyzed several health parameters, including: 1. Cognition and balance assessed using computerized tests, Cogstate, and balance boards to assess memory, processing speed, executive function, and physical stability, and 2. Neuroimaging taken using multimodal magnetic resonance imaging (MRI) to track cortical thickness, white matter microstructure, and functional connectivity.
The study also assessed participants’ brain biochemistry and blood biomarkers, including periventricular white matter total N-acetylaspartate (tNAA) concentration by magnetic resonance spectroscopy, along with plasma levels of glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) to detect markers of astroglial and axonal damage or stress.
Additionally, this study used a structured questionnaire to track each participant’s heading exposure and noted that self-reported values should be interpreted as relative rather than absolute exposure estimates.
Research results
Linear mixed-effects modeling in this study reliably revealed that soccer players showed no statistically significant differences in cognitive abilities, behavioral scales, or balance trajectories compared to their non-contact sport control group counterparts.
Structural and functional neuroimaging metrics were consistent with these findings, establishing that cortical thickness, total gray or white matter volume, white matter microstructure, and default mode network connectivity were not significantly different over time between participants in the soccer and no-contact groups, with P values in the reported cases not reaching statistical significance.
However, analysis of participants’ brain biochemistry and blood biomarkers revealed statistically significant differences between the two cohorts at baseline and preseason. Soccer players initially showed significantly higher concentrations of tNAA (β = -0.379, P = 0.003), GFAP (β = -0.055, P = 0.03), and NfL (β = -0.071, P = 0.01) than controls.
Additionally, this study found that tNAA levels converged between groups throughout the season, with a significant group-by-group interaction (β = 0.047, P = 0.001), decreasing in players and increasing in controls. In contrast, GFAP and NfL levels remained consistently high throughout the season in the soccer cohort, suggesting a parallel trajectory rather than escalation, and remained within the normal physiological range for this age group.
Finally, a comparison of self-reported heading exposure and neurological changes revealed that there was no correlation or significant association between heading exposure and neurological indicators under study in the soccer group.
conclusion
The current REPIMPACT study provides encouraging conclusions that one competitive season of youth soccer is not associated with any detected short-term group-level deleterious changes in adolescents’ cognitive or structural brain health. The findings suggest that elevated baseline biomarkers observed in soccer players may reflect recent exposures, training-related physiology, adaptive or residual responses from previous participation, or other unmeasured factors not specific to the RHI.
However, the authors highlight that while these results provide some reassurance to parents and athletes, the study was limited by its reliance on self-reported exposure and its male-only cohort. Other limitations include the observational, non-randomized design, potential for residual confounding, limited generalizability beyond the European men’s academy setting, exclusion of athletes with physician-diagnosed concussions, and potential lack of power to detect small effects. They highlight the need for large, multi-year studies to establish the chronic effects of soccer on neurological health.
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