In the first study of its kind, former National Football League (NFL) players who lost consciousness due to concussion during their playing days showed key differences in brain structure later in life. The hippocampus, a part of the brain involved in memory, was found to be smaller in 28 former NFL players as compared with a control group of men of similar age and education.
The findings were reported in today’s edition of JAMA Neurology, and they represent the first study to compare the relationship between hippocampal volume, memory performance, and concussion severity.
The study was conducted by a team of neurologists and neuropsychologists from UT Southwestern Medical Center and the Center for BrainHealth at UT Dallas.
“This is a preliminary study, and there is much more to be learned in the area of concussion and cognitive aging,” said Dr. Munro Cullum, Professor of Psychiatry and Neurology and Neurotherapeutics at UT Southwestern, a co-author of the study. “While we found that aging individuals with a history of concussion and loss of consciousness showed smaller hippocampal volumes and lower memory test scores, the good news is that we did not detect a similar relationship among subjects with a history of concussion that did not involve loss of consciousness, which represents the vast majority of concussions,” said Dr. Cullum, who holds the Pam Blumenthal Distinguished Professorship in Clinical Psychology.
Some of the retired NFL players also met criteria for Mild Cognitive Impairment (MCI), a condition that typically affects memory and may lead to dementia. The findings were more pronounced among those who experienced more severe concussions.
The former players ranged from 36 to 79 years old, with a mean age of 58. Twenty-one healthy men of similar age, educational level, and intelligence with no history of concussion or professional football experience served as control subjects.
The results do not explain why the hippocampus was smaller in the athletes who suffered more serious concussions. Some shrinkage is a part of the normal aging process but the reduction is accentuated in MCI and was even more notable in those MCI subjects with a history of concussion accompanied by loss of consciousness. Thus, there appears to be a cumulative effect of concussion history and MCI on hippocampal size and function.
The primary investigator of the study was Dr. John Hart, Professor of Neurology and Neurotherapeutics, and Psychiatry at UT Southwestern, and Medical Science Director and a Professor of Behavioral and Brain Sciences at the Center for BrainHealth at UT Dallas. Dr. Kyle Womack, Associate Professor of Neurology and Neurotherapeutics, and Psychiatry at UT Southwestern, was a contributing author.
Relying on UT Southwestern’s strengths in basic and translational research, the Institute includes scientists focused on improving the understanding of brain damage at the molecular and cellular level, as well as those seeking to identify new therapeutic opportunities, which could ultimately be delivered in clinical care settings.
About this neuroscience research
Funding: The study was funded by The BrainHealth Institute for Athletes at UT Dallas and UT Southwestern’s Texas Institute for Brain Injury and Repair (TIBIR). Founded in 2014, TIBIR embodies a comprehensive and transformative approach to how brain injuries are prevented and treated.
TIBIR is a state-funded initiative to promote innovative research and education, with the goals of accelerating translation into better diagnosis and improving care for the millions of people who suffer brain injuries each year.
Source: Gregg Shields – UT Southwestern Medical Center Image Credit: The image is in the public domain Original Research:Abstract for “Imaging Correlates of Memory and Concussion History in Retired National Football League Athletes” by Jeremy F. Strain, BS; Kyle B. Womack, MD; Nyaz Didehbani, PhD; Jeffrey S. Spence, PhD; Heather Conover, BS; John Hart Jr, MD; Michael A. Kraut, MD; and C. Munro Cullum, PhD in JAMA Neurology. Published online May 18 2015 doi:10.1001/jamaneurol.2015.0206
Imaging Correlates of Memory and Concussion History in Retired National Football League Athletes
Importance: To our knowledge, this is the first study to show an association between concussion, cognition, and anatomical structural brain changes across the age spectrum in former National Football League athletes.
Objective: To assess the relationship of hippocampal volume, memory performance, and the influence of concussion history in retired National Football League athletes with and without mild cognitive impairment (MCI).
Design, Setting, and Participants: This retrospective cohort study assessed differences between groups, mean hippocampal volumes, and memory performance by computing age quintiles based on group-specific linear regression models corrected for multiple comparisons for both athletes and control participants. The study was conducted starting in November 2010 and is ongoing at a research center in the northern region of Texas. This current analysis was conducted from October 9, 2013, to August 21, 2014. Participants included 28 retired National Football League athletes, 8 of whom had MCI and a history of concussion, 21 cognitively healthy control participants, and 6 control participants with MCI without concussion.
Main Outcomes and Measures: Hippocampal volume, age, California Verbal Learning Test scores, and the number of grade 3 (G3) concussions. In addition, the number of games played was examined as an objective variable pertaining to football history.
Results: The mean (SD) age was 58.1 (13) years for the 28 former athletes and 59.0 (12) years for the 27 control participants. Retired athletes with concussion history but without cognitive impairment had normal but significantly lower California Verbal Learning Test scores compared with control participants (mean [SD], 52.5  vs 60.24 ; P = .002); those with a concussion history and MCI performed worse (mean [SD], 37 [8.62]) compared with both control participants (P < .001) and athletes without memory impairment (P < .001). Among the athletes, 17 had a G3 concussion and 11 did not. Older retired athletes with at least 1 G3 concussion had significantly smaller bilateral hippocampal volumes compared with control participants at the 40th age percentile (left, P = .04; right, P = .03), 60th percentile (left, P = .009; right, P = .01), and 80th percentile (left, P = .001; right, P = .002) and a smaller right hippocampal volume compared with athletes without a G3 concussion at the 40th percentile (P = .03), 60th percentile (P = .02), and 80th percentile (P = .02). Athletes with a history of G3 concussion were more likely to have MCI (7 of 7) compared with retired athletes without a history of G3 concussion (1 of 5) older than 63 years (P = .01). In addition, the left hippocampal volume in retired athletes with MCI and concussion was significantly smaller compared with control participants with MCI (P = .03).
Conclusion and Relevance: Prior concussion that results in loss of consciousness is a risk factor for increased hippocampal atrophy and the development of MCI. In individuals with MCI, hippocampal volume loss appears greater among those with a history of concussion.
“Imaging Correlates of Memory and Concussion History in Retired National Football League Athletes” by Jeremy F. Strain, BS; Kyle B. Womack, MD; Nyaz Didehbani, PhD; Jeffrey S. Spence, PhD; Heather Conover, BS; John Hart Jr, MD; Michael A. Kraut, MD; and C. Munro Cullum, PhD in JAMA Neurology. Published online May 18 2015 doi:10.1001/jamaneurol.2015.0206