Some studies have suggested that amateur boxers also damage their nervous systems, but because their shorter bouts allow fewer blows to the head and because they must wear safety equipment, the effects tend to be less severe. Henrik Zetterberg, M.D., Ph.D. at Göteborg University, Sweden, and colleagues obtained spinal fluids from 14 amateur boxers seven to ten days after a bout and again three months later, after a rest from boxing. At the first assessment, the boxers reported how many hits to the head they received during the match and underwent physical and neurologic examinations. The researchers also tested the cerebrospinal fluids of ten healthy men who were not boxers as controls.

Seven to ten days after a boxing match, the group of boxers had higher average levels of chemicals known as neurofilament light protein and total tau than they did three months later. "The cerebrospinal fluid levels of these proteins increase in disorders with neuronal and axonal degeneration and damage, and the increase is known to correlate with the size of the brain lesion," the authors write. "When applied to the results of this study, the increases in neurofilament protein and total tau probably reflect damage to neuronal axons from hits to the head during a bout."

They also had elevated levels of glial fibrillary acidic protein, which indicates damage to the astroglia, specialised cells that surround neurons to insulate and support them. An increase in this chemical was also recently found in patients who experienced severe brain injury, and the levels were linked to the patient's clinical outcome. Levels of all three chemicals were significantly higher in the seven boxers who had sustained more than 15 hits to the head or experienced grogginess during or after a bout, compared with those who had 15 or fewer hits to the head and no grogginess.; Source: JAMA and Archives Journals