A new large-scale study has raised serious concerns about the impact of soccer headers on brain health. Researchers examined 352 amateur adult soccer players and found that repeatedly heading the ball may harm the brain-even without concussions.
The study, the largest of its kind, revealed that players who headed the ball over 1,000 times a year showed microscopic changes in the folds of the brain located behind the forehead and eyes. These structural changes were observed regardless of the player's age or gender.
Moreover, these individuals performed slightly but noticeably worse in memory and learning tests compared to players who headed the ball less frequently.
The findings suggest that repetitive, seemingly harmless headers can cause long-term brain effects, highlighting the need for more awareness and possible reforms in training practices, even at the amateur level.
The study, published September 18 in JAMA Network Open, was conducted in amateur adult soccer players from New York City.
"What's important about our study is that it shows, really for the first time, that exposure to repeated head impacts causes specific changes in the brain that, in turn, impair cognitive function," says study leader Michael Lipton, MD, PhD, professor of radiology and biomedical engineering at Columbia University Vagelos College of Physicians and Surgeons.
The study also gives researchers a brain imaging tool they need to detect these injuries in individuals, learn more about the ways repetitive head impacts affect the brain, and develop treatments.
A second study from Lipton's lab, in press in the journal Neurology, used a different imaging technique to look at the brain and found related damage in the same area.
"The fact that both techniques, looking at two different features, find the same association strengthens our conclusion that these changes are mediating heading's cognitive effects," Lipton says.
Finding signs of brain injury
The researchers used a new imaging technique to look for biomarkers of injury due to heading in an area of the brain previously inaccessible to accurate imaging.
Using diffusion MRI, a technique that examines cellular microstructure and organisation, the researchers imaged the athletes' brains to look at the interface between white and grey matter in the cerebral cortex, the outermost surface of the brain.
"We looked at this interface because white and grey matter have different densities and move at different rates in response to head impact," Lipton says. "That creates shear forces between the two types of tissue, leaving the interface between the two layers vulnerable to injury."
Typical dMRI techniques work well for analysing structures deep inside the brain, but significant hurdles limit their ability to analyse the outer layers-the very areas that may be most susceptible to injury from heading. A graduate student in Lipton's lab, Joan Song, developed a new method to characterise microstructure within the transition zones between grey and white matter in the brain's outer surface.
"In healthy individuals, there's a sharp transition between these tissues," Song says. "Here we studied if an attenuation of this transition may occur with minor impacts caused by heading."
