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.

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).