A couple of decades ago, hardly anyone was worried about the risk of concussions in sports that weren’t boxing. I remember a rugby match I played at school in the 1990s, when a boy lost consciousness for a minute or two after suffering a blow to the head in a crunching tackle. He got plenty of kudos afterward and a tale to share, but zero medical attention.
Times are changing, though, with rising awareness of the harm that can come from repeated blows to the head. Understandably, a great deal of scrutiny has been heaped on the National Football League, by far the biggest pro-sports league in the U.S., over its handling of concussions. Perhaps most dramatically, a 2014 investigation by PBS Frontline reported that the brains of 76 of 79 deceased NFL players showed signs of chronic traumatic encephalopathy (CTE), a form of neurodegeneration that’s associated with repeated injuries to the brain. A year earlier the NFL agreed to pay out hundreds of millions of dollars in compensation to former football players who claimed they suffered brain injuries through the sport.
Soccer, the world’s most-played sport, is increasingly following the same path. Although far less of a contact sport than football, there are natural reasons to be worried: The sport does, after all, involve players deliberately and repeatedly using their heads to strike a fast-moving one-pound ball, and head-to-head collisions between players are frequent as well.
Specific cases have recently stirred up public concerns: For example, last year, the Brazilian soccer star Bellini’s autopsy revealed signs of CTE, as did that of soccer player Patrick Grange of Albuquerque, who died in 2012. Last year current and former soccer players filed a lawsuit against the game’s international governing body, FIFA, calling for rule changes to better protect players from concussion — for example, to limit the number of headers youth players are permitted to make in a game — but this summer a judge found in FIFA’s favor and dismissed the case.
Now a team of neurology researchers, based at Harvard Medical School and universities in Germany, has provided new evidence that will surely intensify fears that playing soccer, just like football or boxing, can cause long-term brain damage.
Writing in Brain Imaging and Behavior, Inga Koerte and her colleagues describe how they scanned the brains of 15 former professional players. The men, with an average age of 49 and free of any history of neurological illness, had all played at least one season of professional soccer, had all started playing in childhood, and were still active players at the time of the brain scans. Their brain scans were compared to those of 15 age-matched former competitive athletes who’d played entirely noncontact sports, such as table tennis, dancing, or running.
The worrying finding is that the soccer players showed significantly more signs of age-related cortical thinning than the controls, especially in brain regions in the parietal and occipital cortices, which are associated with visual and spatial mental functions, among others. That is to say, the soccer players showed a stronger link between greater age and reduced gray-matter volume in these parts of their brains compared to the controls.
Moreover, among the soccer players, the more they reported heading the ball when they played, the more cortical thinning they showed. Also, on a battery of mental tests, the soccer players performed worse than did the controls on a task that requires drawing a complex figure from memory, although their performance was still in the “normal range” expected of healthy people. And the more cortical thinning they showed, the worse they performed on both that test and another that measures mental speed. The researchers think this provides preliminary evidence suggesting that heading the ball repeatedly should be seen as essentially a series of “sub-concussive” episodes, which together with other potential head injuries, such as from player collisions, can eventually lead to harmful brain changes that are associated with premature cognitive decline.
These findings add to others published recently by the same research team that point in a similar direction. For example, Koerte and her colleagues have studied the brains of young soccer players and found signs of subtle changes to the connective tissue in their brains. They’ve also found signs of altered brain chemistry in former professional players. Other researchers have also linked frequency of heading soccer balls with structural changes to the brain.
Based on their latest evidence, the researchers have called for more, larger-scale research to fully document how playing soccer, especially over many years, might affect the brain and whether the kind of brain changes shown here could be linked to neurodegenerative disease such as CTE.
So, how worried should soccer players (and the parents of young soccer players) be by these new results? While there is enough evidence here to justify further research, there are also enough caveats to suggest there is no need for alarm.
Aside from the tiny sample, consider that the researchers had no long-term data on the lifestyle and mental attributes of their participants. For example, perhaps the control participants were better educated and led more healthy lives than the soccer players, meaning that the differences between the groups might have had nothing to do with soccer.
There’s still the correlation between heading rates and cortical thinning to explain, but here it’s worth recognizing the estimates of heading were very inexact. The researchers asked the soccer players to recall how many headers they had performed per week during the past 12 months (not an easy feat of memory), and from this they extrapolated a likely lifetime estimate of headers — the sort of estimate that may well be inaccurate.
It’s also worth bearing in mind the conclusions of a systematic review published this year into all known incidences of chronic traumatic encephalopathy. Joseph Maroon and his co-authors based at the University of Pittsburgh Medical Center and the Institute of Neurology in London warned that speculation about the contribution of contact sports to cases of CTE was wildly out of keeping with the available evidence, which remains extremely limited.
Maroon and his colleagues also cited an important position statement published by the International Conference on Concussion in Sport in 2012, part of which states: “It was further agreed that a cause and effect relationship has not as yet been demonstrated between CTE and concussions or exposure to contact sports.” Maroon’s team says its review of the latest evidence on CTE backs this position.
Concussions in sports should always be taken extremely seriously (make no mistake, a concussion is a form of brain injury), but the sensible response to this latest data on soccer players is not to panic, but to call for the funds to be made available for more long-term and in-depth research into the brain-injury and illness risks associated with both soccer and other sports.
Dr. Christian Jarrett (@Psych_Writer), a Science of Us contributing writer, is editor of the British Psychological Society’s Research Digest blog. His latest book is Great Myths of the Brain.