More Proof of Effects of Pro Fighting on Brain

SAN DIEGO — The volumes of important regions of the brain and the functional connections between them were decreased in amateur and professional fighters with the most experience, MRI scans showed.

Among 104 boxers and 135 mixed-martial arts (MMA) competitors — many of them “cage fighters” — the number of years of pro fighting correlated significantly with reduced volume in the caudate and amygdala, and strong trends were seen toward smaller volumes in the thalamus and putamen, reported Sarah Banks, PhD, of the Cleveland Clinic’s Lou Ruvo Center for Brain Health in Las Vegas.

Resting state functional MRI scans also indicated a correlation between lower connectivity between regions and the amount of fighting experience, she told attendees at the American Academy of Neurology’s annual meeting.

Although the data were from one-time, cross-sectional MRI scans taken from fighters of different ages and experience levels, Banks said the findings pointed toward a dose-response between the number of head blows and important changes within the brain.

Cognitive and other functional deficits in professional fighters have been noted for decades, if not centuries, with the concept of “punch drunk” well known in popular culture. More recently, scientific studies in athletes subject to repeated head blows have pointed to specific abnormalities including but not limited to the tauopathy known as chronic traumatic encephalopathy (CTE).

Much of that research has been based on autopsy findings and studies of retired athletes. Banks and colleagues were interested in what could be learned from living athletes who were still participating in their sports.

In her presentation, Banks noted that Las Vegas — the “Fight Capital of the World — is an ideal place to find subjects for such research. Not only do many professional boxers and cage fighters make the city their home, but local regulations require them to undergo MRI scans in order to secure and maintain a license to fight professionally.

Banks said that her group had also gone to local gyms and fight venues to recruit participants for voluntary participation in a prospective, longitudinal study of brain structure and function in this population.

Longitudinal data are not yet available, but Banks provided a largely qualititative overview of the cross-sectional data collected in the project so far.

Mean age for the overall cohort was 28, with approximately equal numbers of Hispanic, African-American and non-Hispanic white participants. Some 7% were Asian or Pacific Islanders. Mean educational level was about 13 years, with MMA fighters having about one more year of education on average than the boxers.

The average career length at enrollment was 4 years and the mean number of self-reported fights was 11. Banks noted that the frequency of fights varied considerably, such that career length and number of fights did not correlate exactly.

In her group’s analyses, MRI findings were adjusted for intracranial volume, age, education, and race.

The only numerical findings Banks reported were on the relationship between career initiation and length and volumes of particular brain regions of interest: caudate, putamen, thalamus, amygdala, and hippocampus. Up to about year 5 of fight experience, volumes of all these regions did not vary.

With experience beyond year 5, however, volumes declined — most sharply for the caudate. In that region, volumes were 10% lower in participants with 15 years of experience compared with those fighting for 5 years or less (P<0.001).

Volumes were lower by about 5% for the amygdala and putamen (P=0.036 and 0.067, respectively).

There was a lesser trend toward smaller volumes with experience in the thalamus (P=0.092) and no hint of a relationship in the hippocampus.

Caudate volumes and years of fighting experience were more strongly related in participants who said they began fighting in earnest at age 15 or younger, Banks said. In that subgroup, caudate volumes were smaller by 0.37% for each bout reported by participants. In contrast, the reduction was only 0.10% per bout for participants who said they began fighting after age 15.

Participants with relatively longer careers and higher frequency of fights also tended to show reduced connectivity between the basal ganglia and other brain regions, she said.

She pointed out that the basal ganglia has been identified in previous studies of chronic head injury in athletes as a locus for abnormalities. In particular, much of the CTE pathology seems to be centered there.

Session co-moderator Scott McGinnis, MD, of Brigham and Women’s Hospital in Boston, commented that longitudinal data from study participants would be telling. Banks agreed and added that her group planned to expand the study to a larger group in the near future.

Banks also indicated that the study team had been recruiting healthy controls, but there were not enough of them yet for a meaningful comparison of results.

• Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.
• The volumes of important regions of the brain and the functional connections between them were decreased in amateur and professional fighters with the most experience.
• Note that resting state functional MRI scans also indicated a correlation between lower connectivity between regions and the amount of fighting experience.
  
  Source:
  http://www.medpagetoday.com/meetingcoverage/aan/38037