Women who play football are more at risk of injury from heading the ball than their male counterparts, according to a study published in the journal Radiology.
Researchers found that female players had more extensive changes to brain tissue after repetitive heading of the ball, suggesting that sex-specific guidelines may be necessary to help prevent head injuries in the sport.
Heading is already known to be associated with abnormalities in the brain's white matter that are similar to those seen in patients with traumatic brain injury.
"Researchers and clinicians have long noticed that women fare worse following head injury than men, but some have said that's only because women are more willing to report symptoms," said study leader Dr Michael L. Lipton from the Albert Einstein College of Medicine. "Based on our study, which measured objective changes in brain tissue rather than self-reported symptoms, women do seem more likely than men to suffer brain trauma from heading soccer balls."
Dr Lipton and colleagues used diffusion tensor imaging, an advanced MRI technique, to assess microscopic changes in the brain's white matter in 49 male and 49 female amateur football players aged from 18 to 50 years. Both groups reported a similar number of headings over the previous year.
The scans showed that the volume of damaged white matter in women football players was five times greater than for male players. The women also had eight brain regions where greater levels of heading were associated with microstructural abnormality compared with only three regions in men.
However, the changes in the brain were subclinical, meaning they were not associated with altered brain function.
It's not yet known why women might be more sensitive to head injury, but differences in neck strength, sex hormones or genetics could play a role.
"We don't have enough information yet to establish guidelines to protect the players," Dr Lipton said. "But by understanding these relationships -- how different people have different levels of sensitivity to heading -- we can get to the point of determining the need for gender-specific recommendations for safer soccer play."