Ask Onix
Long-Term Brain Risks in Contact Sports
Professional soccer players and American football athletes face significantly higher risks of developing neurodegenerative diseases like Alzheimer's, Parkinson's, and motor neurone disease due to repeated head impacts, recent studies reveal.
Historical Warnings and Modern Findings
The dangers of repeated head trauma in sports were first documented nearly a century ago. In 1928, pathologist Harrison Martland described a condition known as "punch drunk" in boxers, characterized by staggering gait and mental confusion. This later became known as dementia pugilistica, a form of dementia linked to repeated blows to the head.
Decades later, research expanded beyond boxing. In 2002, former England and West Bromwich Albion soccer player Jeff Astle died at 59 from early-onset dementia. Post-mortem examinations revealed chronic traumatic encephalopathy (CTE), a degenerative brain condition caused by repeated head injuries. Similarly, NFL player Mike Webster died at 50 after exhibiting Parkinson's-like symptoms, with CTE confirmed in his brain.
CTE: A Growing Concern
Willie Stewart, a neuropathologist at the University of Glasgow, explains that CTE is uniquely tied to a history of head injuries. "The best way to identify potential CTE is to ask if someone has played football or rugby. If a professional footballer has dementia, the likelihood of CTE is very high," he says.
A 2023 study by Ann McKee at Boston University analyzed the brains of 376 former NFL players and found that 91.7% had CTE. While this sample may not represent the general population-since players suspecting CTE were more likely to donate their brains-it underscores the severity of the issue. CTE has also been diagnosed in athletes from baseball, cycling, and ice hockey.
Soccer and Neurodegenerative Risks
Stewart's Football's InfluencE on Lifelong health and Dementia risk (FIELD) study compared nearly 8,000 former Scottish professional soccer players to 23,000 general population controls. The findings were stark: soccer players were five times more likely to develop Alzheimer's, four times more likely to suffer from motor neurone disease, and twice as likely to develop Parkinson's. Overall, their risk of dying from neurodegenerative disease was 3.5 times higher.
Defenders, who head the ball most frequently, faced the highest risks, while goalkeepers showed risks similar to the general population. The study also found that longer careers correlated with greater risk, ranging from a twofold increase for shorter careers to a fivefold increase for the longest.
How Heading Damages the Brain
Michael Lipton, a radiologist at Columbia University, used MRI scans to study brain changes in amateur soccer players. His research found that frequent headers showed damage in the orbitofrontal cortex, an area critical for memory and learning. The white matter in this region, which acts like the brain's network cabling, is particularly vulnerable to stretching and disruption from sudden impacts.
"The force from heading causes the brain to compress, twist, and deform inside the skull, straining the axons," Lipton explains.
Michael Lipton, Columbia University
Players who headed the ball over 1,000 times per year exhibited the most damage, particularly at the junction between white and grey matter, where differing densities create shear forces during impacts.
Preventive Measures and Future Research
While the exact mechanisms linking head impacts to neurodegenerative diseases remain unclear, theories include chronic inflammation, blood vessel damage, and neuronal degeneration. Stewart suggests that repeated injuries may trigger persistent inflammation or leaky blood vessels, allowing harmful substances to enter the brain.
Efforts to mitigate risks are underway. Stanford University researchers are developing football helmets with liquid shock absorbers to reduce head impacts by 30%. In the UK, heading has been banned in youth soccer, and training sessions now limit heading drills to reduce unnecessary impacts.
"Footballers may head the ball 70,000 times in their careers, but only a few thousand occur during matches. The rest happen in training-let's minimize those," Stewart says.
Willie Stewart, University of Glasgow
Despite these measures, Stewart acknowledges the challenge: "If we stopped banging our heads against things, the risk would disappear. But practically, that's hard to enforce."
Unanswered Questions
Lipton's research highlights that while brain damage is evident in young, healthy players, not all will develop neurodegenerative diseases. Genetics and lifestyle factors may play a role, but further research is needed to understand why some individuals are more vulnerable than others.
