A new study at Columbia University Irving Medical Center links soccer heading-where players hit the ball with their heads to direct it during play-to a decline in brain structure and function over a two-year period. The research is being presented for the first time at the annual meeting of the Radiological Society of North America (RSNA) in Chicago this week .
While previous research has examined adverse effects on the brain related to soccer heading at a single point in time, the new findings are the first to show brain changes over two years. "These findings add to the ongoing conversation and contentious debate as to whether soccer heading is benign or confers significant risk."
"There is enormous worldwide concern for brain injury in general and the potential for soccer heading to cause long-term adverse brain effects in particular," said senior author Michael L. Lipton, MD, PhD, professor of radiology at Columbia University's Vagelos College of Physicians and Surgeons and affiliate professor of biomedical engineering at Columbia University.
"A large part of this concern relates to the potential for changes in young adulthood to confer risk for neurodegeneration and dementia later in life."
Study design
The study included 148 young adult amateur soccer players, with a mean age of 27. Participants were assessed for verbal learning and memory and underwent magnetic resonance imaging (MRI) at the time of enrollment and again two years later.
Participants also filled out a specialized questionnaire, developed by the research team, to determine how many headers they performed. Two-year heading exposure was categorized as low, medium, and high.
The researchers used an MRI technique called diffusion tensor imaging (DTI) and a newer technique called neurite orientation dispersion density imaging (NODDI), which characterize the microstructure of the brain by tracking the movement of water molecules through the tissue. "By measuring how uniform the movement of water is through brain tissue, we can assess whether brain tissue structure is normal or abnormal," says Lipton, "and we can see the effects on brain structure with increasing numbers of head impacts."
Study results
Compared to the baseline test results, the high-heading group (over 1,500 headers in two years) demonstrated measureable changes in brain microstructure similar to findings seen in mild traumatic brain injuries.
"This is the first study to show a change of brain structure over the long term related to sub-concussive head impacts in soccer," Lipton says.
High levels of heading were also associated with a decline in verbal learning performance on a memory test. In contrast, participants who engaged in low or no heading demonstrated an improvement in verbal learning performance over a two year period.
"These findings add to the ongoing conversation and contentious debate as to whether soccer heading is benign or confers significant risk."
Related findings
Dr. Lipton and colleagues also presented a second study in which they analyzed heading over 12 months prior to assessment with DTI and testing verbal learning performance. The study looked at 353 amateur soccer players between the ages of 18 and 53.
Unlike previous research that has focused on deep white matter regions, this study employed a new approach assessing change of DTI parameters to evaluate the integrity of the interface between the brain's gray and white matter closer to the skull.
The researchers found that the normally sharp gray matter - white matter interface was blurred in proportion to high repetitive head impact exposure, consistent with injury at the gray matter - white matter interface. Further analysis showed that the change in brain structure at the gray matter - white matter interface plays a causal role in the association of greater heading with worse cognitive performance.
"Our new approach addresses a brain region that is susceptible to injury but has been neglected due to limitations of existing methods," Lipton says. "Application of this technique has the potential to disclose the extent of injury from repetitive heading, but also from concussion and traumatic brain injury, to an extent not previously possible."
Next Steps
Research shows that changes in brain structure and function are associated with high levels of soccer heading. In a new study that is just underway, Lipton and colleagues will assess the competing effects of fitness and head impacts on the brain by looking at soccer players, athletes who never participated in contact sports, and nonathletes.
"Soccer players and their parents have been rightly warned about the potential risks of heading in soccer, but it leads to mixed messages about the wisdom of playing the sport," says Lipton. "This grant will allow us to determine soccer's tradeoffs with respect to brain health so that people can make informed decisions, and we can establish evidence-based guidelines for heading."
