The world's largest study of the brains of dead professional athletes has found that the majority were suffering from a degenerative brain condition before they died, giving a sobering glimpse into the potential long-term impact of violent contact sport.
Of the 85 brains Boston University researchers studied, 68 were found to have chronic traumatic encephalopathy (CTE), a disease brought on by repetitive hits to the head and linked to depression, memory loss, aggression and dementia. Half of those 68 were former professional football players; 16 more played football as their primary sport.
Football faces a reckoning over safety issues at all levels. Concern over the prevalence of head injuries in youth football has forced rule changes in leagues across the United States. The National Football League is staring down a massive lawsuit brought this summer by thousands of former players touched by concussions and brain injuries sustained during their careers – a legal case that National Hockey League officials must be watching closely.
The study is to be published on Monday in the scientific journal Brain. A copy was obtained by The Globe and Mail.
While the prevalence of CTE is unknown, the Boston researchers say their work shows a clear link between the disease and football – and potentially other sports played by donors in the study, including rugby, wrestling and hockey. The brains of five former hockey players were analyzed. Four were found to have CTE. Most played the role of enforcer. They were NHL stars Reggie Fleming, Derek Boogaard, Bob Probert and Rick Martin.
Donors in the study also included two NFL Hall of Famers, tight end John Mackey and running back Ollie Matson, and former NFL and CFL running back Cookie Gilchrist. All were found to have advanced CTE.
"I don't think we can ignore it any longer. It's not going to go away if we pretend it doesn't exist. It does exist," said Anne McKee, a professor of neurology and pathology at Boston University and the study's lead author. "And if you talk to any of [their] family members, they will tell you it's devastating. Truthfully, working on this disease is really heartbreaking."
The study is the first to classify the disease into degrees of severity, highlighting four stages as it slowly marches through the neurological system over decades.
Initially, CTE begins with damaged neurons in one area of the brain, and symptoms might include headaches or problems concentrating. In Stage 2, subjects may grapple with depression and impairment of their short-term memory, and then eventually progress to Stage 3, which includes difficulty with multi-tasking, planning and judgment. Stage 4 includes full-blown dementia.
Within the sample, which also included the brains of former soldiers, the authors also found that one-third of the CTE cases were diagnosed with additional degenerative diseases, including Alzheimer's and Lewy body disease. Of the donors, seven died from suicide.
In most cases, the disease was the most severe in the athletes who died in their 60s, 70s and 80s, confirming what researchers already suspected: it is degenerative.
However, the researchers were perplexed to discover that a small number of the older donors had low-level CTE despite being exposed to brain trauma as young athletes. This suggests that a mystery factor – possibly genetic or environmental – may stop the disease from advancing in some people.
"It definitely opens up the question of why do the majority of people relentlessly progress with this disease, but not everybody. What is it unique about those people that don't relentlessly progress? And that holds great hope, if we can figure it out, for treatment and prevention," said Robert Cantu, co-author of the paper and co-founder of the Sports Legacy Institute in Boston.
CTE results from what Dr. Cantu called "total brain trauma" – which includes multiple hits to the head that cause the brain to rattle off the skull, something that doesn't always result in a concussion. Generally, athletes suffered the repetitive brain trauma over many years. Certain sports (such as boxing and football), and certain positions played (linebackers in football and enforcers in hockey), appear more prone to these sorts of repetitive brain traumas, Dr. Cantu said.
While scientists say it is likely that CTE is rare, they still don't know many things, such as who is most susceptible, how it can be diagnosed while players are still living, and what can be done to prevent or treat it.
Dr. Cantu emphasized that people should not assume there is a direct link between CTE and concussions, especially if the concussions are diagnosed and treated properly. In fact, he said, some of the brains found to have CTE came from people who had never been diagnosed with a concussion.
"Just because somebody's had three, four, five concussions, don't suddenly think you're going to wind up with CTE – that's not the way it works," Dr. Cantu said.
He added that concussions should be taken seriously and treated properly to prevent other serious medical conditions, including post-concussion syndrome and second-impact syndrome.