Heading a soccer ball alters the brain, new research spearheaded by the University of Sydney has found, despite having no immediate impact on cognition.
The findings of a world-first experiment add to evidence suggesting heading a ball in the world’s most played sport can impact the brain, even when concussion doesn’t occur. The research was published today in the Sports Medicine - Open journal.
The results signal a need for further research into heading’s long-term effects, its authors say, as the higher risk of dementia among former professional footballers becomes more apparent. They also give cause to investigate protective interventions including nutrition and cannabinoids.
The study is the first randomised controlled trial measuring the impact of heading using Magnetic Resonance Imaging (MRI) on soccer players.
Soccer heading study
Under supervision from Professor Iain McGregor in the University’s Faculty of Science, a team of researchers performed brain-related assessments on 15 male, adult soccer players soon after the players headed a soccer ball 20 times in as many minutes.
Using state-of-the-art MRI facilities at Neuroscience Research Australia (NeuRA), the researchers were able to look for regional changes in brain structure, function and chemistry. Blood and cognitive function tests were also performed. The study used a tightly-controlled setting, with balls launched at a constant speed from a machine. Each participant also completed a control condition involving kicking, rather than heading, a ball, allowing researchers to isolate the effects of heading.
The MRI scans identified subtle but measurable changes. These included altered chemistry in a region of the brain involved in motor control and decreased electrical conductivity across several areas. These findings suggest heading affects the brain’s energy use/needs and how information is transmitted through white matter.
The blood samples also showed elevated levels of two proteins: GFAP and NFL. These proteins are currently considered some of the best available blood biomarkers of brain injury and future dementia risk. However, the changes associated with heading were much smaller than those typically seen in these conditions.
No cognitive impairment was observed following heading.
“This study does not demonstrate heading causes dementia,” said Dr Nathan Delang, who led the research as a PhD candidate at Griffith University and is now a postdoctoral researcher at the University of Queensland.
“Our take from the higher presence of these proteins, and the study overall, is that heading the ball can cause subtle disruption to brain cells, even without obvious symptoms.
“Elevated levels of these biomarkers indicate brain cells have been disturbed at a microstructural level. The clinical and long--term significance of such small elevations is still being studied—particularly in relation to how much, and what pattern, of exposure might lead to effects on brain structure and function.”
The next step is to understand whether these changes accumulate over time, and what that might mean for player health in the long run.
Dr Danielle McCartney
Soccer ball safety
Some countries, including the United States and the United Kingdom, are phasing in restrictions on heading, including banning the practice among young players. Australia has not introduced a such a ban, but discussions are ongoing regarding the safety of heading in youth sports.
“These findings suggest that even routine, symptom-free heading can produce subtle changes in the brain. The next step is to understand whether these changes accumulate over time, and what that might mean for player health in the long run,” said research co-author Dr Danielle McCartney, from the University of Sydney’s Lambert Initiative for Cannabinoid Therapeutics.
“In the meantime we’re adding to calls for soccer players to exercise caution and perhaps consider whether extensive heading is necessary, particularly in training.”
The research for this paper was undertaken at the University of Sydney’s Lambert Initiative for Cannabinoid Therapeutics. Dr Delang led the research as a PhD candidate at Griffith University.
About the funding and ethics of this research
This study was primarily supported by funding from the Lambert Initiative for Cannabinoid Therapeutics (a philanthropically funded centre for medicinal cannabis research at the University of Sydney). Additional funding support was provided from Griffith University and Monash University.
The donor did not have any input into the investigation.
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