A new study shows different effects in the brain for younger current fighters compared with older, retired fighters. The study is published in the December 23, 2019, online issue of Neurology, the medical journal of the American Academy of Neurology.
Both the current and former fighters had a loss of brain volume. Current fighters had volume loss in areas of the brain suggestive of injury from axonal shearing. Retired fighters had volume loss suggestive of a progressive disease process, such as chronic traumatic encephalopathy (CTE) or Alzheimer disease (AD).
There were no significant differences in the scores on the thinking and memory tests among the groups of current and retired fighters and nonfighters. However, when the current fighters were divided into participants with brain volume loss and participants without, they found that those with brain volume loss had worse scores on 2 of the thinking tests for processing speed.
The current boxers lost an average of 145 mm3 in volume per year, compared to a loss of 100 mm3 for the current mixed martial arts fighters and a gain of 43 mm3 for the nonfighters. The retired boxers did not show changes in the hippocampus and thalamus of the brain. Instead, they showed brain volume loss in the areas of the left and right amygdala and the right hippocampus. These are areas of the brain that are affected in diseases such as AD and CTE. The retired boxers lost an average of 43 mm3 per year, compared to a gain of 10 mm3 for the nonfighters.
For the right hippocampus, the average volume at the start of the study was 2,350 cubic millimeters (mm3). For the left thalamus area of the brain, the average volume at the beginning of the study was 3,773 mm3.
“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, MD, 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 involved 50 current boxers with an average age of 29 and an average of 5 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 8 fights. They were compared to 31 nonfighters 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 group. He also noted that a few women were involved in the study: 1 retired boxer, 2 current boxers, 10 MMA fighters and 5 of the nonfighters. The participants had brain scans and took tests of memory and thinking skills at the beginning of the study and again each year for at least 2 years.
Evanthia Bernitsas, MD
Robert Shavelle, PhD, FAACPDM; Jordan Brooks, PhD, MPH; David Strauss, PhD, FASA; and Amytis Towfighi, MD
Karissa Gable, MD