CHICAGO—Using diffusion tensor imaging (DTI) to study the effects of soccer 'heading,' researchers have found that players who head the ball with high frequency have brain abnormalities similar to those found in traumatic brain injury (TBI) patients. Results of the study were presented on Nov. 30 at the 97th Scientific Assembly and Annual Meeting of the Radiological Society of North America (RSNA).
Soccer is the most popular sport worldwide, with more than 250 million players. Heading, in which players field the soccer ball with their head, is an essential part of the game and the focus of many training drills. Amateur and college ball speeds can hit 35 miles per hour, with professional ball speeds exceeding 60 miles per hour.
"Heading a soccer ball is not an impact of a magnitude that will lacerate nerve fibers in the brain," Michael L. Lipton, MD, PhD, associate director of the Gruss Magnetic Resonance Research Center at the Albert Einstein College of Medicine and medical director of MRI services at Montefiore Medical Center in New York City, said in a statement. "But repetitive heading could set off a cascade of responses that can lead to degeneration of brain cells."
“Even ‘minor’ head trauma can cause brain injury and long-term problems, and injury to white matter axons is characteristic of these problems,” Lipton said during the press conference at RSNA.
Abnormally low white matter fractional anisotropy (FA) has been associated with cognitive impairment in TBI patients, according to the study abstract, so the researchers set out to use DTI to measure FA in soccer players and see if a threshold level for heading exposure exists above which evidence of white matter injury is detectable. If it was detectable, the researchers wanted to see if they could establish a threshold for heading that would not lead to injury.
Lipton and colleagues conducted DTI on 38 healthy, amateur soccer players (five women), with an average age of 30.8 years old, all of whom have played the sport competitively since they were at least five years old.
The researchers estimated how often each soccer player headed the ball on an annual basis and then ranked the players based on heading frequency. They then compared the brain images of the most frequent headers with those of the remaining players and identified areas of the brain where FA values differed significantly.
"Between the two groups, there were significant differences in FA in five brain regions in the frontal lobe and in the temporooccipital region," said Lipton. "Soccer players who headed most frequently had significantly lower FA in these brain regions."
Results showed that exceeding a threshold heading frequency of 1,000 to 1,500 per year may result in brain abnormalities similar to those seen in TBI patients. “Frequency is key, as having one injury followed by another injury shortly thereafter might be more damaging than injury spread out over a longer period of time,” Lipton said.
The five regions identified by the researchers are responsible for attention, memory, executive functioning and higher-order visual functions.
"Given that soccer is the most popular sport worldwide and is played extensively by children, these are findings that should be taken into consideration to protect soccer players," said Lipton, who called the findings “provocative.”
He concluded that soccer heading may be a form of mild TBI. “As with mild TBI in general, the adverse effects are likely to go unrecognized or misattributed,” Lipton said. While he stressed that he was not banning heading in soccer, Lipton and his colleagues are suggesting that these findings call for public health interventions to reduce exposure to excessive heading and minimize the adverse effects.
“Although this is a small, preliminary study, the mechanism of injury can truly be related to heading, and not to another aggressive activities,” he said.
Introducing imaging to the widespread soccer player population would be an expensive proposition, Lipton told Health Imaging, but cognitive tests might be more practically beneficial.