In a recent study published in JAMA Network Open, researchers examined the brain architecture and neurophysiological features of adolescent soccer players.
The neurological effects of head injuries on adolescent soccer players are unclear. While American football can promote teamwork, repeated subconcussive hits, particularly in young athletes, can cause neurological problems.
Studies have shown that collision sports athletes have reduced cortical thickness, but current high school and college football players show greater reduction in brain volume and cortical thinning in frontotemporal regions. Resting-state functional magnetic resonance imaging (RS-fMRI) functional connectivity indicated neurophysiological changes caused by repeated head injuries.
About the Study
In the present study, researchers used advanced neuroimaging techniques to assess brain anatomy and neurophysiology in high school soccer players and participants in non-contact sports.
The team paired adolescent soccer players with control subjects participating in non-contact sports such as tennis, swimming, and cross-country from five high school sports programs, based on age, school, and male gender. They performed imaging studies between May and July 2021 and in the following year, analyzing the data between February and November 2023.
The study participants were exposed to soccer and non-contact sports. The study findings included structural MRI data examining cortical sulcal depth, thickness, gyrification, RS-fMRI data examining amplitude of low-frequency fluctuations (ALFF), resting-state functional connectivity (RS-FC), and regional homogeneity (ReHo).
The team consisted of individuals aged 13 to 18 years, currently members of a high school soccer team or a non-contact sports team. They excluded individuals with a history of moderate to severe traumatic brain injuries (TBI), control athletes participating in organized contact sports, and MRI contraindications.
Initially, the team created a reference volume and its skull-stripped version, registering the BOLD reference to T1-weighted images. They excluded individuals with head movements and framewise displacement of more than 3.0 mm and 3.0 degrees from the fMRI analyses, and reproduced the BOLD time series in its original, natural space. The team selected the dorsolateral prefrontal cortex (DLPFC) due to its involvement in brain injuries as a region of interest (ROI). The team considered age, number of previous brain injuries, body mass index (BMI), Patient Health Questionnaire (PHQ-9) scores for depression, Generalized Anxiety Disorder (GAD-7) scores for anxiety, and intracranial volume as variables in the study.
Overall, 275 males (205 soccer players; 189 White (92%), five Asians and eight Black or African American; 70 control subjects; 64 White (92%), four Asians and one African American or Black were analyzed. The average age of the participants was 16 years. Compared to the control players, soccer players showed significant cortical thinning, particularly in the anterior occipital regions such as the precentral gyri on the right side and the superior frontal gyri on the left side.
Conversely, soccer players showed increased cortical thickness in the left cingulate cortex and in the caudal cingulate cortex in the anterior and posterior regions of the right hemisphere, respectively. Soccer players exhibited greater sulcal depth in the precuneus, precentral gyri, and cingulate cortex, particularly in the lower part of the parietal lobe and in the caudal cingulate cortex regions of the anterior part of the right hemisphere, in comparison to control subjects.
Comparatively, soccer players had increased gyrification in various regions of both hemispheres, including the frontoparietal areas, cingulate cortex, lingual gyrus, and precuneus. In contrast, the team observed reduced gyrification in the pericalcarine, superior temporal gyri, pars orbitalis gyri, and caudal cingulate cortex of the anterior brain, compared to control subjects.
The team found significantly lower ALFF values in the cingulate cortex and frontal lobes of soccer players, including the left triangular, superior, and middle frontal gyri; precentral gyrus; anterior and middle cingulate cortex; and bilateral insular regions. Conversely, they observed increased ALFF in the medial occipital areas of the left hemisphere of soccer players, including the calcarine and lingual gyri.
Similarly, the team noted significantly higher regional homogeneity in the occipitotemporal brain regions of soccer players compared to control subjects, including the sulcus calcarinus, middle, lingual, and inferior occipital gyri, as well as inferior and middle temporal gyri. In contrast, the team observed markedly lower regional homogeneity in the right and left precentral gyri and in the medial brain regions, including the bilateral posterior and middle cingulate cortex, putamen, and insula.
Overall, the study revealed cortical thinning in the frontal and occipital areas, thickening in the cingulate cortex, greater sulcal depth, and increased gyrification in the brains of developing soccer players compared to control subjects. Local brain activity patterns indicated lower ALFF in the frontal region and higher ALFF in the occipital region. Brain signal coherence was similar, with lower ReHo in the medial and frontal areas and higher ReHo in the occipitotemporal regions. The study findings also highlighted the continuous growth and maturation of the gyri and sulci of the cortex, which are essential for the developmental trajectory from childhood to adolescence.