A smaller hippocampal volume, which is the area of the brain important for memory, was observed in a group of collegiate football players who had experienced a concussion and was also associated with length of football experience, according to a study published on May 13 by JAMA.

The hippocampus is especially sensitive to moderate and severe traumatic brain injury (TBI), and recent research indicates that it could also be vulnerable to mild TBI. Data on the long-term anatomical and cognitive consequences of concussion on young athletes are lacking, so lead author Rashmi Singh, PhD, of the Laureate Institute for Brain Research in Tulsa, Okla., and colleagues examined the relationship between years of football playing experience and history of concussion with cognitive performance and hippocampal volume in collegiate football players.

“In animal models, repetitive mild TBI injuries rapidly induce reactive gliosis and neuronal death in the hippocampus, resulting in cognitive impairment and memory deficits,” wrote the authors.

Singh et al conducted a cross-sectional study that included 25 players with a history of clinician-diagnosed concussion, 25 collegiate football players without a history of concussion and 25 healthy controls. Their brain volumes were quantified through the use of high-resolution anatomical MRI, and scores on a computerized concussion-related cognitive test were used to assess the athletes.

Results revealed that collegiate football athletes had smaller hippocampal volumes than the healthy control participants. Players with a history of concussion had a smaller volume than those that did not and in both athlete groups there was a statistically significant inverse relationship between left hippocampal volume and number of years of football played.

Behavioral testing demonstrated no significant differences between athletes with and without a concussion history on five cognitive measures. However, an inverse correlation between years of playing football and reaction time was observed.

“The present study design limits our ability to dissociate among the many possible factors in these hippocampal volume findings, but our study should serve as an impetus for future longitudinal research to investigate the neuroanatomical and cognitive changes in young contact-sport athletes. The clinical significance of the observed hippocampal size differences is unknown at this time,” wrote Singh and colleagues.

They suggest the need for further longitudinal research to establish the temporal relationships of their findings.