A season-long study of teen soccer players offers reassurance on short-term brain health, but elevated preseason biomarkers show why the heading debate is far from settled.
Study: Youth Soccer Participation and Brain Health Outcomes in Adolescent Athletes. Image Credit: Master1305 / Shutterstock
In a recent study published in JAMA Network Open, researchers conducted a longitudinal investigation to determine how competitive youth soccer, particularly heading a soccer ball, is associated with brain health outcomes in the developing brain. The study tracked 129 male athletes over a single season and evaluated participants’ cognitive performance, behavior, balance, and neuroimaging metrics.
Encouragingly, study findings did not detect statistically significant short-term group-level changes in brain structure, function, or cognitive health compared to noncontact sport athletes. These findings indicate that a single season of competitive youth soccer was not associated with detectable adverse changes in the measured neurological domains. However, distinct preseason differences in neurological biomarkers between soccer players and controls indicate the need for expanded, multiyear tracking.
Background
Soccer has long been considered the world’s most popular sport. Current estimates highlight that more than 22 million adolescents take part in soccer in some form, competitive or recreational, globally. However, the unique act of "heading," or striking the ball with the head, is increasingly fuelling medical debate over athlete safety.
Researchers and clinicians have raised concerns that repetitive head impacts (RHIs), subconcussive blows that do not trigger full concussions, could jeopardize rapid brain maturation during adolescence. These concerns are partly based on data from retired professional players, which has previously linked prolonged “heading” exposure to elevated risks of neurodegenerative diseases later in life.
Unfortunately, scientific evidence regarding immediate, short-term effects on youth remains scarce, limiting its interpretation in younger competitive soccer athletes. This uncertainty has driven parental anxiety and prompted precautionary heading restrictions in several countries.
About the Study
The present “REPIMPACT” study aimed to address this knowledge gap and inform future sports medicine by systematically evaluating whether a single competitive soccer season alters adolescent neurological health.
The REPIMPACT study was a longitudinal, prospective, multicenter cohort study conducted across three European sites: 1. Munich, Germany, 2. Leuven, Belgium, and 3. Oslo, Norway. The study sample cohort comprised 129 male athletes aged 14-16 years, including 82 academy-level soccer players who practiced at least 3 times weekly and 47 age-matched controls who practiced noncontact sports such as swimming, athletics, cycling, and racket sports.
The study notably excluded any participants with a history of physician-diagnosed concussions, thereby reducing the confounding effects of head injuries on the effects of routine play. Study data were collected in three distinct phases: 1. Preseason, 2. Postseason, and 3. Two months following the end of the season under investigation.
The study analyzed several health parameters, particularly: 1. Cognition and balance, evaluated using computerized testing, Cogstate, and balance boards to evaluate memory, processing speed, executive function, and physical stability, and 2. Neuroimaging, captured using multimodal magnetic resonance imaging (MRI) to track cortical thickness, white-matter microstructure, and functional connectivity.
The study also evaluated participants’ brain biochemistry and blood biomarkers, including periventricular white matter total N-acetylaspartate (tNAA) concentrations via magnetic resonance spectroscopy, alongside plasma levels of glial fibrillary acidic protein (GFAP) and neurofilament light chain (NfL) to detect markers of astroglial and axonal injury or stress.
Additionally, the study tracked each participant’s exposure to heading using structured questionnaires, noting that self-reported values should be interpreted as relative rather than absolute exposure estimates.
Study Findings
The study’s linear mixed-effects modeling reassuringly revealed that soccer players showed no statistically significant differences compared to their noncontact sport control-cohort counterparts in cognitive capabilities, behavioral scales, or balance trajectories.
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 did not differ significantly, longitudinally, between soccer and noncontact group participants, with reported example P values not reaching statistical significance.
However, analyses of participants’ brain biochemistry and blood biomarkers revealed statistically significant differences between the two cohorts at baseline and preseason. Soccer players initially exhibited 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.
Furthermore, the study found that over the season, tNAA levels converged between groups due to a significant group-by-time interaction (β = 0.047, P = 0.001), declining in players and rising in controls. In contrast, GFAP and NfL levels remained consistently higher in the soccer cohort throughout the season, suggesting parallel trajectories rather than escalation, and remained within the normal physiological range for this age group.
Finally, contrasting self-reported heading exposure volume against neurological changes revealed no correlation or significant association between heading volume and any neurological metric under investigation in the soccer group.
Conclusions
The present REPIMPACT study encouragingly concludes that one competitive season of youth soccer was not associated with detected harmful short-term group-level changes in adolescent cognitive or structural brain health. Its findings suggest that the elevated baseline biomarkers observed in soccer players may reflect recent exposure, training-related physiology, adaptive or residual responses from prior participation, or other unmeasured factors not specific to RHIs.
However, the authors highlight that while these findings offer measured reassurance to parents and athletes, the study was limited by its reliance on self-reported exposure and an exclusively male cohort. Other limitations included the observational, nonrandomized design, potential residual confounding, limited generalizability beyond European male academy settings, exclusion of athletes with prior physician-diagnosed concussion, and possible underpowering to detect small effects. They emphasize the need for large-scale, multiyear studies to establish the chronic effects of soccer on neurological health.
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