Study leader Sanna Neselius of Sahlgrenska Academy at the University of Gothenburg in Sweden, said boxers in the study competed at the top-level of Swedish boxing and all had fought at least 47 bouts. None had lost on a knockout, and only one mentioned symptoms after a bout (headache), the study said.
Neselius, in collaboration with the Swedish Boxing Federation, said the study showed repeated blows to the head in the boxing ring can produce a release of brain injury markers to the brain fluid. It has a similar effect to what is seen with after other types of head trauma, as well as in neurological illnesses such as Alzheimer´s disease, Neselius said.
"Our study shows that after bouts, some of the boxers had elevated concentrations of four different proteins in the brain fluid, which all signal damage to the brain's nerve cells. Moreover, two of the proteins were still elevated after a period of rest," Neselius said in a statement.
The study published in the journal PLoS ONE found as many of 80 percent of the boxers exhibited protein changes that indicate brain damage.
"The brain injury markers were elevated for 80 percent of the Olympic boxers directly after a bout as a result of minor brain damage," Neselius said. "That the brain fluid markers were elevated even after weeks of rest for some of the boxers can be interpreted as the damage had yet not healed or that some damage will remain."