correlates of memory and concussion history in retired national football league

Strain JF., Womack KB., Didehbani N., Spence
JS., Conover H., Hart J. Kraut MA., Cullum CM. JAMA Neurology. 2015; ahead of

Take Home Message: Prior
concussion that resulted in loss of consciousness is a risk factor for
decreased hippocampal regions and mild cognitive impairment later in life.

memory dysfunction (for example, Alzheimer’s disease, mild cognitive
impairment) after a concussion injury remains poorly understood and it is still
debated whether concussions cause these impairments. Changes in the brain (for
example, hippocampal
atrophy) may be related with a history of concussions and mild cognitive
impairment and learning more about these relationships may help us understand
the relationship between concussions and memory impairments. Therefore, the
authors measured hippocampal volumes with Functional Magnetic Resonance Imaging, performed neuropsychological tests, and
collected descriptive information to determine the relationship of memory
performance with hippocampal volume coupled with the influence of concussion
history in 28 retired National Football League (NFL) athletes (36-79 years of
age, education ranged from 15-18 years, estimated IQ ranged 92-126, 2-15 years
of NFL experience, and 8 had mild cognitive impairment with concussion history). Twenty-one cognitively healthy participants were included as a comparison group
for NFL athletes. The comparison group was matched for education and IQ (44-77
years of age, education ranged from 12-20 years) and had no history of
concussion or past college or professional football participation. In addition,
6 age and sex matched participants with mild cognitive impairment were
recruited from an Alzheimer’s disease Center for comparison with athletes who
had a history of concussion and a diagnosis of mild cognitive impairment. The
authors used 5 neuropsychological tests: California Verbal Learning Test, Rey-Osterrieth Complex Figure Test, Boston Naming Test,
and Semantic Object Retrieval Test. Three variables were related with hippocampal volume
bilaterally in athletes without memory impairments: age, California Verbal
Learning Test total score, and grade 3 concussions (required loss of consciousness after concussion, 1997 American Academy of Neurology guidelines). NFL athletes with both concussion history and mild cognitive
impairment performed worse on the California Verbal Learning Test compared with
both control groups. The 11 retired NFL athletes who reported no grade 3
concussions showed similar hippocampal volumes compared with control
participants across age distributions; however, 17 retired NFL athletes with at
least one grade 3 concussion had lower mean hippocampal volumes compared with
control participants. Additionally, NFL athletes with a career of 120 or more
games in the NFL had a lower mean left hippocampal region compared with control
participants. Athletes with fewer than 120 games did not differ from control
participant’s hippocampal volume.

study demonstrated a quantitative relationship between a history of concussion
with a loss of consciousness and a loss of hippocampal volume or lower verbal
memory performance later in life. The cognitive battery included many tests for
cognitive impairment, but only verbal memory was related with hippocampal
volume. One criteria for a grade 3 concussion is loss of consciousness, which
has been associated with poorer long-term outcomes, and this study found that
athletes reporting at least one grade 3 concussion demonstrated a reduction in
hippocampal volumes and lower California Verbal Learning Test scores. It’s
important to note that this study cannot tell us if a concussion causes these
changes in the hippocampus or verbal memory performance, but can only tell us
that they are related. Knowledge of hippocampal volumes and verbal memory
performance prior to head injury would be interesting for future studies to help
us understand how concussions effect these measures. Medical professionals
should note the importance of verbal memory testing following a concussion as
well as monitor athletes with a loss of consciousness and concussion history
more closely for changes in verbal memory.

Questions for Discussion:
Should a concussion grading system be considered again? Do you think long-term,
follow-up appointments may be helpful for athletes that are at risk for poorer
outcomes after suffering a concussion?

by: Jane McDevitt, PhD
by: Jeff Driban


Strain JF, Womack KB, Didehbani N, Spence JS, Conover H, Hart J Jr, Kraut MA, & Cullum CM (2015). Imaging Correlates of Memory and Concussion History in Retired National Football League Athletes. JAMA Neurology PMID: 25985094