Brain scans of former American football players reveal signs of white matter injury, according to research into the lasting effects of repetitive head impacts in sport.
The finding is viewed as significant because until now it has been difficult to identify such damage in the brain until after death. The latest work suggests that markers of injury could be detectable using specialised MRI scans, allowing doctors to study, and potentially diagnose, such damage more readily.
“Our results are exciting because they show that white matter [scans] might capture long-term harm to the brain in people who have a history of repetitive head impacts,” said Michael Alosco, a neuropsychologist at Boston University School of Medicine and lead author of the study.
The findings come as sporting bodies continue to grapple with the question of how to improve safety as evidence has emerged linking repetitive impacts, such as during tackles in rugby or heading the ball in football, to cognitive problems such as dementia.
Alosco said that further work would be needed before the scans could be used to diagnose individuals, but that it would provide an immediate research tool to help illuminate the link between sports such as American football, boxing and rugby, and conditions such as dementia.
The study involved 75 people who were exposed to repetitive head impacts and had undergone scans as part of medical assessments. This included 67 American football players, eight other athletes in sports such as football and boxing and military veterans. Of the American football players, each of whom played an average of 12 years, 16 athletes played professionally and 11 played semi-professionally.
All donated their brains to research after their death in order to advance research into the issue. Researchers then looked at medical records, including scans which were done while the athletes were still alive. Participants had scans of their brains at an average age of 62, and the average age at death was 67.
Of the participants, 64% were judged to have had dementia prior to death, based on a discussion with their loved ones. Autopsies showed that 71% had chronic traumatic encephalopathy (CTE), a neurodegenerative disease associated with repetitive head impacts, including those from contact sports, that can progress to dementia.
The study, published in the journal Neurology, revealed that white matter hyperintensities – bright spots on images of the brain’s white matter that connects neurons – were correlated with evidence of small vessel disease and other indicators of damage to the brain’s white matter in postmortem investigations. The volume of white matter hyperintensities on scans also correlated with impairment scores on performing daily tasks, completed by caregivers of brain donors, and were associated with more years of playing football.
There was also a link with the accumulation of tau protein in the brain, another biomarker for degenerative brain disease.
Alosco said that white matter tracts – long fibres that connect different brain regions – could be particularly vulnerable to injury during high impact sports, adding: “Perhaps as they get older these [injuries] persist or get worse with age.”
A limitation of the study was that it used scans taken during medical examinations, mostly of people who were already suffering dementia, rather than tracking athletes through time to test whether the scans could predict future cognitive damage.
Michael Grey, a neuroscientist at the University of East Anglia, who is co-leading a trial on concussion in sport, said it would not be feasible to use this kind of scan widely as a diagnostic tool, but that being able to study athletes during their lifetimes could help understanding of what repetitive impacts do to the brain. “It’s an important advance, there’s no doubt about that,” he said. “Pathology alone is not going to solve this issue.”