An average of ten professional boxers died every year as the result of injuries in the 1900s. Retirement is often followed by memory problems, anxiety, dementia and other manifestations of brain damage. The degree to which the brain has been damaged can be measured and monitored after a match during the phase when it is particularly vulnerable to fresh injuries.
Researchers at Sahlgrenska Academy have compiled evidence about head injuries from contact sports that has been accumulating over the past 85 years.
The first scientific study to show that boxers sustained chronic brain damage was published in 1928. Subsequent studies included hockey, American football and other contact sports, currently estimated as causing 300,000 cases of brain damage every year in the United States alone.
Researchers at Sahlgrenska Academy, University of Gothenburg, Sweden, have reviewed every scientific study (more than 160 in all) published about head injuries among athletes since 1928.
“There is a lot we still don’t know about sports-related brain damage,“ Professor Kaj Blennow says. “The long-term purpose of our review is to improve both diagnosis and treatment.”
According to the study, an average of ten professional boxers died every year in the 1900s due to injuries sustained in the ring, the great majority after having been knocked out. The study also found that American football players can suffer as many as a thousand blows to the head in a single season. Such blows are dangerous even if no loss of consciousness or brain damage is involved.
“Research has shown that approximately one-third of all professional boxers experience memory loss or speech disorders after retirement,” Professor Henrik Zetterberg says, “while MRI studies have found that three out of four have physical brain abnormalities. Repeated blows to the head during an athletic career are also associated with anxiety, personality changes, impaired learning capacity and other chronic symptoms.”
Amateur boxers are less likely to face such problems later in life as a result of head injuries.
“A fairly intensive debate is under way about the reasons for this discrepancy,” Professor Blennow says. “Studies frequently point out that amateur boxing matches have fewer rounds and referees are more likely to call them when there is a clear risk of injury.”
The Sahlgrenska researchers review shows that a punch by a professional boxer can be as powerful as a 13 pound bowling ball traveling at 18 miles per hour. Blows that cause the head to rotate, leading to brain damage when the long axons of the neurons are torn, are the most dangerous.
“The neurological damage caused by a knockout can last for several months, long after the boxer has stopped noticing any discomfort,” Professor Zetterberg says.
The researchers concluded that relatively little is known about the neurobiological repercussions of engaging in a contact sport – both diagnostic criteria and effective treatment methods are lacking. Studies conducted by Professors Blennow and Zetterberg have found that blood samples taken after a boxing match and other special biomarkers can be used to detect brain damage but that they are still not clinically available.
The researchers also showed that the severity of brain damage after a match can be measured in the cerebrospinal fluid. Boxers with high levels may be tested repeatedly until normal results indicate that they can return to sparring or the ring. Avoiding new blows to the head may be important during the phase when the brain is particularly vulnerable to fresh damage.
Specific interventions are already available to protect athletes, especially professional boxers, more effectively.
“One logical intervention would be to prohibit blows to the head,” Professor Blennow says, “especially among young boxers, whose nervous systems are more vulnerable. Another option would be for professional boxers to fight fewer rounds or be required to wear head protection, as well as reinforcing the padding in their gloves.”
The study, entitled The Neuropathology and Neurobiology of Traumatic Brain Injury was published in Neuron in December 2012.
