NFL retirees may not be the only footballers at risk for chronic traumatic encephalopathy. Heading the ball may put players of the world’s most popular sport, soccer, at risk for the neurodegenerative condition as well, according to two recent studies. In the most detailed pathological study on CTE in soccer players to date, Janice Holton and Tamas Revesz at University College London found a high incidence of CTE in 14 former players who had developed dementia. As detailed in the February 15 Acta Neuropathologica, all these athletes had headed the ball thousands of times during their careers yet had, at most, one diagnosed concussion. The authors suggest that repeated sub-concussive impacts may have been causal in their disease. In a separate study, published online February 1 in Neurology, scientists led by Michael Lipton, Albert Einstein College of Medicine, New York, found that in 222 young, active amateurs, heading the ball associated with concussion-like symptoms. Together, these studies hint at the dangers of heading at different points in a player’s career, Lipton told Alzforum. “Numerous repeated impacts that may not be recognized as concussion may add up to a problem down the road,” he said.
CTE is a progressive degenerative disease that vitiates the brains of some boxers, American football players, hockey players, and soldiers, all of whom may experience severe concussions as part of their jobs (for a review, see McKee et al., 2016). Little is known about the condition in people who play soccer. The average player suffers but one or two concussions over a decades-long career, though they may endure numerous other accidental hits to the head, for instance by banging against another player, crashing to the ground, or thudding up against a goalpost. They also intentionally head the ball dozens of times a week, adding up to thousands of sub-concussive impacts over a career.
Could these repetitive hits to the head lead to CTE? Recent media attention has swirled around that question. The death in 2002 of 59-year-old former center forward and English international Jeff Astle was attributed to CTE, and four of the eight surviving members of the English team that won the 1966 World Cup now suffer from dementia. So far in the literature, only four case studies have reported brain damage in retired soccer players: Three of those people had CTE and one had Alzheimer’s pathology (McKee et al., 2014; Hales et al., 2014; Grinberg et al., 2016; Bieniek et al., 2015). No one had analyzed a group of players.
The project on retired soccer players got its start in the 1980s with co-author and psychiatrist David Williams, then of the psychiatric hospital at Cefn Coed, in Swansea, Wales. Williams treated a 58-year-old retired professional soccer player who had advanced dementia. As this patient had been a skilled header of the ball, Williams wondered if repetitive head impacts could explain his cognitive impairment and early disease onset. Williams and colleagues, including first authors Helen Ling and Huw Morris, followed this patient, as well as 12 other retired soccer players and one avid amateur referred to the clinic for progressive cognitive impairment, over the next 30 years. The researchers collected data on the patients and got information from caregivers on concussions, memory symptoms, and career history, and took clinical and demographic data from medical records.
All had started playing in childhood or adolescence. Six had experienced a single concussion in a game. Five of them had lost consciousness from the concussion. They all experienced cognitive impairment—the onset ranged from 40 to 78 years—that lasted about a decade. Each had one or more accompanying symptoms, such as motor impairment, hallucination, or behavioral changes. Twelve had a CT or magnetic resonance imaging scans soon after onset of their neurological symptoms, which revealed cortical atrophy.
Six brains were donated for postmortem analyses. All had TDP-43, Aβ, and tau pathology, with Lewy bodies in one case. Four had true CTE as defined by recent NINDS criteria, marked by tau aggregation in the neurons, astrocytes, and cell processes around blood vessels, particularly in the cortical sulci (McKee et al., 2016). Tau pathology turned up in other areas of the remaining two patients, and all had dilation of the third ventricle, features supportive of a CTE diagnosis.
All six postmortem patients also had holes in the septum pellucidum, a thin membrane in the middle of the brain that can tear in response to mechanical stress. “This is perhaps the most striking pathological finding of all,” wrote Simon Vann Jones, Franklyn Community Hospital, Exeter, U.K., to Alzforum. He was not involved in the study. Since damage to the septum is uncommon in the general population, and since these players had at most only one documented concussion, chronic low-level trauma was likely responsible for this rupture, he said. Vann Jones also noted that all six postmortem patients experienced significant personality changes soon after dementia diagnosis, suggesting such shifts may be a common clinical marker of CTE. However, the study yields no insight about how common CTE is in soccer players, he cautioned in an email (see full comment below). Even so, he found this a valuable study. “The findings raise an alarm for all sports and activities that involve low-level head trauma and should encourage further measures to mitigate this risk.”
Ling said the results fit with prior, larger studies that suggest head impacts without concussions are associated with CTE (Stein et al., 2015). The group is currently searching for biomarkers in blood, urine, or saliva that reflect brain trauma and predict CTE in athletes, she said.
“This is confirmation that CTE can occur in soccer players,” wrote Kaj Blennow, University of Gothenburg, Sweden, to Alzforum. He called for longitudinal studies on players of different contact sports to determine how frequently CTE occurs, which factors—such as concussion severity or length of career—contribute to its development, and which might protect from the condition.
“The paper fits perfectly with evidence that head injuries in football, hockey, and soccer are reasonably dangerous and could lead to CTE,” said Robert Friedland, University of Louisville School of Medicine, Kentucky. This also supports the emerging idea that multiple concussions are not necessary for brain damage to occur, he said.
Heading Symptoms Fly Under the Radar
Lipton’s study highlights the dangers amateur players may face when heading a soccer ball. He and first author Walter Stewart of Sutter Health Research in Walnut Creek, California, surveyed 222 active, amateur players aged 18 to 55 about how often in the past two weeks they had headed a ball versus how many times they had hit their heads against other players, the ground, or goalposts. Stewart and colleagues found that both intentional and unintentional hits to the head led to symptoms such as headache, dizziness, and nausea. Risk tripled in the quartile of players who headed the most, compared to those who reported no head impacts. Unintentional impacts had their own effect, with a single event tripling risk for symptoms and two or more leading to sixfold higher instance.
“The papers and guidelines in the literature suggest that heading is not a common cause of recognizable concussion,” Lipton told Alzforum. “We are challenging that by saying heading does cause concussive symptoms.” However, that’s not the biggest problem, he said. “The question is, what does repeatedly having your head impacted over years do to your brain? Precious little has been done to understand that.”
Recent research and lawsuits have led to a U.S. Youth Soccer ban on heading in players younger than 10, with limits imposed on those aged 11 or 12. Heading is unlikely to be eliminated from the game entirely, Lipton said, but more research into how much is tolerable to the brain and who is most susceptible to damage will help make the game safer for players. “As with many of the dangers we are exposed to, the evidence suggests that heading is not an all-or-nothing bad thing,” said Lipton. “Guidelines that prevent people from overdoing it are much more likely to gain traction than an absolute ban.”
Robert Stern, Boston University, agreed that a ban on heading wouldn’t be warranted based on this one paper, and added that he doesn’t think parents should prevent kids from playing, either. “We need to conduct a lot more research on how great an impact heading has first.” However, this study adds more evidence that repetitive sub-concussive trauma may lead to a neurodegenerative disease, he said.
In response to recent research, including these two papers, a spokesperson for FIFA, the word governing body of soccer, said, “To our best knowledge, there is currently no true evidence of the negative effect of heading or other sub-concussive blows. FIFA will continue to monitor the situation of head injuries, maintaining constant contact with current and ongoing studies regarding long-term neurocognitive changes, both in male and female football players. Protecting the health of football players is and will remain a top priority in developing the game.”—Gwyneth Dickey Zakaib
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