Amateur Boxing Linked to Neurochemical Disturbances

BY DIANA MAHONEY
Elsevier Global Medical News

BOSTON (EGMN) - Participation in amateur boxing is directly associated with neuronal and astroglial damage, according to a small study presented today at the annual meeting of the American Academy of Neurology.

Dr. Max Albert Hietala of Sahlgrenska University Hospital, Goteborg, Sweden, presented data from a longitudinal investigation of 11 male and 3 female amateur boxers showing significant increases in biochemical markers of acute neuronal and axonal injury and of astroglial injury following a fight, compared with those detected in the same individuals after a 3-month rest from boxing.

The mean levels of neurofilament light protein, total tau, and glial fibrillary acidic protein in the cerebrospinal fluid (CSF) of the 14 boxers enrolled in the study were, respectively, 845 ng/L, 449 ng/L, and 541 ng/L at 7-10 days following a bout, compared with 208 ng/L, 306 ng/L, and 405 ng/L after 3 months, Dr. Hietala reported. All these increases were statistically significant. Furthermore, the increases at 7-10 days after a bout were significantly higher among the seven boxers who received more than 15 hits to the head, compared with those who reported few hits, he said.

Increases in neurofilament light protein and total tau - both important constituents of neuronal axons - have been observed in conditions with neuronal and axonal degeneration and damage in direct correlation with the size of the brain lesion. Glial fibrillary acidic protein is an intermediate filament protein that is found in glial cells and astrocytes, and studies have linked increases in this protein to astrocyte reactions to brain damage from acute head trauma.

The fact that the increases in the CSF levels of these biomarkers were most pronounced in the boxers who received many hits to the head, and that the levels showed signs of normalizing after 3 months, suggests a direct link between the changes and brain trauma resulting from hits to the head, according to Dr. Hietala. "This study shows clearly that multiple hits to the head give rise to brain tissue damage," he said. "More than 15 hits is approximately equivalent to a lacunar infarction. It's also equivalent to an exacerbation of multiple sclerosis. This happens every time the boxer enters the ring."

The damage is potentially increased by an order of magnitude among professional boxers, Dr. Hietala noted. "This study was conducted with amateur boxers, for whom special rules apply, such as short rounds, extra padded helmets, and gloves," he said.

The investigators also compared the boxers' CSF biomarker levels with those of 10 healthy, nonathletic male control subjects and determined that immediately after a bout the boxers had higher levels than the nonboxers of neurofilament light protein and glial fibrillary acidic protein, Dr. Hietala said. After 3 months, significant differences in neurofilament light protein levels persisted. When analyzed based on number of hits, those boxers who received few hits had biomarker levels that were statistically indistinguishable from those in the healthy controls, he said.

Unlike evidence from previous studies demonstrating Alzheimer-like pathologic findings, there were no significant changes in the CSF biomarkers of the amateur boxers in this study reflecting the pathogenic processes that have implicated in Alzheimer's disease, including elevated phosphorylated tau concentration, decreased beta-amyloid protein 1-40 concentration, or the ratio of beta-amyloid protein 1-42 to beta-amyloid protein 1-40, according to Dr. Hietala.

To determine whether soccer players experience similar neuronal effects from "heading" the soccer ball, the investigators conducted a separate study comparing the neurochemical biomarkers of the 10 nonathlete controls to those of 23 players, including 10 who headed the ball at least 10 times and 13 who headed the ball at least 20 times from a 30-meter corner kick 7-10 days prior to lumbar puncture. "We found no neurochemical evidence for neuronal injury caused by heading," Dr. Hietala reported.

The take-home message from these investigations "is that lumbar puncture and CSF analysis may be a useful tool for clinicians to use in the assessment and management of boxers and other athletes who sustain head injury [in the course of their sport]," Dr. Hietala concluded.

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