BOSTON -- Even amateur boxers risk brain damage from repeated blows to the head during a single fight, Swedish researchers reported here.
BOSTON, May 2 -- Even amateur boxers risk brain damage from repeated blows to the head during a single fight, Swedish researchers reported here.
In a small study, amateur boxers showed significantly elevated levels of neurofilament light protein in cerebrospinal fluid (CSF). said Max Hietala, M.D., Ph.D., of the Sahlgrenska University Hospital in Goteborg, and colleagues. The protein is a marker for neuronal damage from shearing stresses.
Although punch-drunk syndrome, or dementia pugilistica, has been known for nearly a century, it has been difficult to pinpoint specific neuronal changes that could account for the neural and cognitive problems boxers develop, Dr. Hietala commented at the American Academy of Neurology Meeting.
Dr. Hietala and his colleagues hypothesized that proteins released into the CSF after neuronal shearing and axonal damage could be markers for potential brain damage.
"The mechanical forces in boxing are quite horrendous," Dr. Hietala said. "In less than a 10th of a second, the head, the brain, gets a hit of about 600 kilograms [in force]. If you get an uppercut, the acceleration-deceleration of the brain would give rise to a shearing of neurons, and the neurons would die and release proteins within the spinal cord."
To test this theory, the investigators drew CSF from 14 amateur boxers (11 men and three women) seven to 10 days after an organized match, which in Sweden lasts a maximum of four rounds, and again after three months of rest.
They measured for levels of neurofilament light protein, and total tau protein, as well glial fibrillarcy acidic protein, a marker for astroglial injury. They compared the levels they detected with CSF levels of the proteins in 10 healthy, non-athletic controls.
They found "a leakage of all the components in the brain that are in the neurons and even in the astrocytes," Dr. Hietala said.
They also found that levels of all three markers were significantly elevated compared with controls:
The researchers also found that the tougher the beating, the higher the levels of proteins. Boxers who had received more than 15 blows to the head during a single bout had levels of neurofilament light protein that were seven to eight times the levels of boxers whose heads were struck less often, and this difference was statistically significant. Levels of glial fibrillary acid protein, but not total tau, were also significantly elevated among the boxers who sustained the highest levels of head assaults.
With the exception of neurofilament light protein, there were no significant differences between boxers after 3 months of rest from boxing and the non-athletic control subjects.
Dr. Hietala noted that the protein leak into CSF occurred even though amateur boxing is tightly regulated in Sweden, with requirements for extra-thick padded headgear.
Noting the need for verification in longitudinal studies, Dr. Hietala nonetheless recommended the use of lumbar puncture (when it can be performed by trained neurologists or other specialists) as a screening tool for neural markers among athletes who sustain blows to the head on a regular basis.
"It's painless, it's not dangerous, and it's very much equivalent to taking a venous sample," he said. "We urge, and we very much want to spread the use of taking lumbar punctures."
For soccer players, however, this may not be necessary, When the investigators extended their study to soccer players, repeatedly heading the ball did not appear to have the same deleterious effects on the brain, Dr. Hietala commented in a press briefing.
They recruited medical students from the University of Goteborg to take corner kicks and head them into the net, dividing the students into those who headed fewer than 20 balls, and those who headed more than 20.
"One of these soccer plays headed the ball 57 times, repeatedly," Dr. Hietala said. "He got wooziness, dizziness, he threw up and had all the signs of a pure concussion. When we did a lumbar puncture on him and measured the number of neurofilaments, it wasn't elevated. So our conclusion is that heading a ball in soccer is not dangerous."
Heading the ball is a planned motion in which the neck is positioned and the forehead, the hardest part of the cranium, takes the force of the balls impact, he noted.