Utility of providing a concussion definition in the assessment of concussion history in former NFL players.

Objective: Former National Football League (NFL) players' working knowledge of concussion has not yet been evaluated, despite this population being a major clinical research target due to the association between repetitive head impacts (RHI) and long-term clinical impairments. This study examined former NFL players' understanding of the current concussion definition, and the association between number of concussions with, clinical function. Methods: 95 former NFL players (mean age = 55.29; mean NFL year = 8.10) self-reported number of concussions before being provided with a concussion definition and after being read a modern definition of concussion. Subjects reported number of concussions with loss of consciousness (LOC), Principal Component Analysis of a battery of tests generated behaviour/mood, psychomotor speed/executive function, and verbal and visual memory factor scores. Restilts: Post-definition number of concussions (median = 50); Was five times the pre-definition (median = 10; p < 0.001). Greater pre- (p = 0.019) and post-definition concussions (p = 0.036) correlated with worse behaviour/Mood scores, after controlling for years of football played, with specific effects for depressive symptoms and impulsivity. LOC did not account for variance beyond number of concussions. Conclusions: Practitioners and clinical researchers should provide a definition of concussion in the assessment of concussion history in former football players to facilitate accuracy and standardization.