Women football players are far more at risk from heading the ball than men, according to research.
Scientists found that low-level brain damage linked to repeatedly heading the ball was more than twice as extensive in female players.
Gender-specific guidelines may be necessary to avoid football-related head injuries in women, the US researchers suggested.
Lead scientist Professor Michael Lipton, from Albert Einstein College of Medicine in New York City, said: “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.
“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.”
An estimated 30 million women and girls play football worldwide, according to the sport’s world governing body Fifa.
Prof Lipton’s team used a type of scan called diffusion tensor imaging (DTI) to look at the brains of 98 male and female players ranging in age from 18 to 50.
Both groups reported similar numbers of headers in the previous year – an average of 487 for men and 469 for women.
Women reported similar numbers of headers as man (Daniel Hambury/PA)
DTI detects subtle levels of damage by measuring water diffusion in white matter, which consists of nerve fibres linking different brain regions.
Loss of uniform diffusion is an indication of poor microstructural integrity and brain damage.
Women had eight brain regions where more experience of heading balls was associated with worse scan scores, compared with three for men.
Co-author Todd Rubin, a PhD student at Albert Einstein College, said: “The findings add to the growing body of evidence that men and women express distinct biological responses to brain trauma.”
Writing in the journal Radiology, the researchers speculate that neck strength, sex hormones or genetics may explain the difference in brain vulnerability.
They pointed out that the levels of brain damage measured were sub-clinical and did not produce obvious signs of altered thinking ability.