Background: Repeated concussions are associated with postconcussive symptoms including memory impairment. Professional athletes in contact sports seem to be at greater risk of persistent symptoms due to repeated concussions. We used volumetric analysis to test whether repeated concussions have delayed effects in terms of decreased hippocampal volume and poor memory performance in former professional football players. Methods: Participants were 38 retired Canadian Football League (ex-CFL) players (age=56.0+12.9 years) and 21 healthy male controls (age=48.3+10.7 years) without history of concussion. Controls from the Alzheimer's Disease Neuroimaging Initiative database (ADNI) (N=179) were used for validation because of our small control sample size. The number of self-reported concussions in the ex-CFL group ranged from 0-48. Participants underwent a 3T T1-weighted structural MRI scan and a Rey Auditory Verbal Learning Test (RAVLT) to assess verbal memory. Scans were pre-processed using a standard pipeline: image intensity non-uniformity correction, intensity range normalization (0-100), stereotaxic registration and non-linear warping to an average template brain (Montreal Neurological Institute ICBM-152). Volumetric analysis was performed and hippocampal volumes were correlated with age, adjusting for intracranial volume, and with RAVLT word recall scores, adjusting for age. Results: The ex-CFL players showed a significant association between age and left hippocampal (LH) (r=-.60, p<.001) and right hippocampal (RH) volume (r=- .57, p<.001), whereas in controls this trend was non-significant (LH r=-.32, p=.16; RH r=-.33, p=.14, respectively). A similar but significant association was found between age and both the LH and RH volumes (r=-.40, p<.001; r=-.36, p<.001, respectively) in controls from the ADNI database. In the ex-CFL group, we found a correlation between volume of the LH and RH and word recall performance on the RAVLT short delay (r=.45, p=.01; r=.42, p=.02 respectively) and long delay (r=.41, p=.02; r=.38, p=.04 respectively). No association was observed between LH and RH volumes and RAVLT short or long delay scores in our control group. Conclusions: Our data suggest a stronger effect of age on hippocampal volume in ex-CFL than in individuals without a history of concussion. The hippocampal volumes in the ex-CFL were related to performance on a verbal memory task. Multiple concussions may contribute to accelerated aging of the hippocampus that could explain some of the cognitive complaints reported by athletes.
Misquitta, K., Dadar, M., Tarazi, A., Ebraheem, A., Multani, N., Khodadadi, M., … Tartaglia, M. C. (2016). P4-216: Reduction in Hippocampal Volume is Associated With Age and Memory Deficits in Retired Professional Football Players. Alzheimer’s & Dementia, 12, P1110–P1110. https://doi.org/10.1016/j.jalz.2016.06.2308