A new study of boxers and mixed martial arts (MMA) fighters finds that both current and retired fighters show a loss of brain volume, but in different ways.
In the current fighters, the volume loss is in brain regions that suggest it is due to injury, a phenomenon that occurs when nerve fibers are torn as the brain gets shaken inside the skull.
In the retired fighters, the volume loss was in brain areas that suggest it is due to the progressive disease process seen in neurodegenerative diseases such as chronic traumatic encephalopathy (CTE) or Alzheimer’s disease.
CTE is a rare brain condition found in athletes and others with a history of repeated head traumas. Symptoms include memory loss and thinking problems as well as emotional and behavior changes such as aggression.
“More research is needed to confirm these findings and to see if this pattern of loss of brain volume continues over a longer time period, but the results suggest that people with repeated head impacts may experience different processes in the brain at different times,” said study author Charles Bernick, M.D., of the Cleveland Clinic Lou Ruvo Center for Brain Health in Las Vegas, and a member of the American Academy of Neurology.
“Ideally, future studies would build on these results and help us identify ways to predict irreversible injury so we could reduce the risks for these professional athletes before it’s too late.”
The study, published in the journal Neurology, involved 50 current boxers with an average age of 29 and an average of five fights; 23 retired boxers with an average age of 45 and an average of 38 fights; and 100 mixed martial arts fighters with an average age of 29 and an average of eight fights.
The fighters were compared to 31 non-fighters with an average age of 31 who had no history of head trauma, military service or participation at the high school level or higher in a sport in which head trauma can often occur, such as football or soccer.
Bernick said too few retired MMA fighters took part in the study to form a separate group. He also noted that a few women were involved in the study: one retired boxer, two current boxers, 10 MMA fighters and five of the non-fighters.
The participants underwent brain scans and completed memory and thinking tasks at the start of the study and again each year for at least two years.
Compared to the non-fighters, the current boxers had a greater average yearly rate of loss of brain volume in the areas of the left thalamus, the mid-anterior corpus callosum and the central corpus callosum.
In the MMA fighters, a similar pattern was seen, but to a slightly lesser extent, in the left thalamus and the central corpus callosum, Bernick said.
For the left thalamus area of the brain, the average volume at the beginning of the study was 3,773 cubic millimeters. The current boxers lost an average of 145 cubic millimeters (mm3) in volume per year, compared to a loss of 100 mm3 for the MMA fighters and a gain of 43 mm3 for the non-fighters.
The retired boxers did not exhibit changes in these regions. Rather, they showed brain volume loss in the areas of the left and right amygdala and the right hippocampus, regions commonly affected in diseases such as Alzheimer’s and CTE.
For the right hippocampus, the average volume at the start of the study was 2,350 mm3. The retired boxers lost an average of 43 mm3 per year, compared to a gain of 10 mm3 for the non-fighters.
Bernick noted that these changes in brain volumes were relatively small. “More research is needed to determine if these small changes could help us predict what will happen for individual athletes,” he said.
Overall, the study found no significant differences in the scores on the thinking and memory tests among the groups of current and retired fighters and non-fighters.
However, when they split the current fighters into two groups — those with brain volume loss and those without — they discovered that those with brain volume loss had worse scores on two of the thinking tests for processing speed.
One limitation of the study is that fighters volunteered to take part, so it’s possible that people having problems or concerns about their health might be more likely to take part in the study.
Source: American Academy of Neurology