Soccer headers — when players of the sport pass the ball with their heads rather than their feet — are, for more than 250 million active players worldwide, a source of repetitive impacts to the head. This is not a particularly good thing for the brain.
The force of a header is concentrated at the front of the skull behind the eyes and can affect white matter close to the brain's surface.
To understand what sort of effect headers might have on the brain, researchers looked at the brains of about 350 amateur soccer players with an average age of 26 and 77 athletes with an average age of 23 who played non-collision sports.
The study showed that headers are associated with damage in the folds of the white matter near the cortex of the brain in young soccer players.The young adult soccer players who reported the most headers had about 3,152 headers a year; those who reported the fewest had about 105 headers.
The soccer players were surveyed about the number of headers they sustained over the previous year. They were divided into four groups based on the number of headers: those who reported the most headers had about 3,152 headers a year and those who reported the fewest had about 105 headers.
The team, led by researchers at Columbia University and the Albert Einstein College of Medicine, used diffusion MRIs to see how water molecules moved through the folds of white matter near the brain's cortex. Water molecule movement became more disorganized in the groups who reported more headers, suggesting these soccer players sustained more damage to the white matter than those reporting fewer headers and athletes in non-collision sports.
Study participants also took tests of thinking and memory skills to see how headers affected their cognitive function. Athletes who did poorly on these tests reported more headers than those who did better. Damage to the folds in what is called the orbitofrontal region at the front of the brain, just above the eye sockets, particularly affected the relationship between repeated headers and cognitive function.
The orbitofrontal region and prefrontal cortex in general play an important role in making decisions, regulating emotions and forming memories.
“While taking part in sports may have many benefits, including possibly a reduced risk of cognitive decline, repetitive head impacts in contact sports like soccer may offset these potential benefits," Michael Lipton, corresponding author on the study, told TheDoctor.
Lipton said he and his team did not expect the location of the damage from soccer headers to be so specific, and he noted that the location of the damage closely matches what is seen in the neurodegenerative disease chronic traumatic encephalopathy (CTE). Whether the damage will progress to CTE in these soccer players, however, is an open question.
The accumulation of tau protein in the brain that is characteristic of CTE marks the late stages of a long process that is preceded by other changes in the brain, Lipton explained. The researchers may have been assessing the early phase of that process, which may or may not progress to CTE.
“Most people who have repetitive head impact don't develop CTE,” explained Lipton, a professor of radiology at Columbia University Irving Medical Center. “We don't know what makes people develop CTE.”
The study shows an association between heading and changes to an area at the front of the brain, but it was designed only to provide evidence of this correlation; it could not prove that headers cause the damage they found or that it affected cognitive function.Water molecule movement became more disorganized in the groups who reported more headers, suggesting damage to the white matter.
Lipton and his team are currently considering additional ways to image the brain to learn more about the pathology associated with repetitive head impacts. They are also evaluating different types of cognitive tests which may give them more information about the effects of repetitive head impact on brain function.
The study and a related editorial are published in Neurology.
