Loss of Consciousness is Associated with Increased Neurocognitive Intra-Individual Variability Following Sports-Related Concussion

Abstract

Abstract Purpose Traditional markers of concussion severity, including loss of consciousness (LOC), retrograde amnesia (RA), and post-traumatic amnesia (PTA), have been inconsistently associated with neurocognitive performance following sports-related concussion. The purpose of this study was to evaluate whether LOC, RA, and PTA influence a particular aspect of post-concussion cognitive functioning—across-test intra-individual variability (IIV). Methods Concussed athletes (N=119; 77.3% male) were evaluated, on average, 8.55 days post-concussion (SD=11.27; Mdn=4 days) via clinical interview and neuropsychological assessment. Primary outcomes of interest included two measures of IIV-an average standard deviation (ASD) score and a maximum discrepancy (MD) score-computed from 18 norm-referenced variables. Results A one-way ANCOVA adjusting for time since injury revealed a significant effect of LOC on the ASD (F(1, 116)=6.78, p=.010, ηp2=.055) and MD (F(1, 116)=5.65, p=.019, ηp2=.046) scores, such that athletes with LOC displayed significantly greater IIV than athletes without LOC. In contrast, measures of IIV did not significantly differ between athletes who did and did not experience RA or PTA (all p>.05). Conclusion LOC, but not RA or PTA, was associated with greater variability, or inconsistencies, in cognitive performance following concussion. This suggests that LOC may be a relevant consideration when evaluating post-concussion cognitive dysfunction. IIV has recently been established as a sensitive measure of cognitive functioning in a variety of clinical samples and has been associated with underlying neurobiological integrity. Taken together, our results implicate LOC as a possible contributing factor of less efficient cognitive functioning following concussion and may help detect athletes at risk for poor clinical outcomes.