Loss of Consciousness is Associated with Elevated Cognitive Intra-Individual Variability Following Sports-Related Concussion

Abstract

Objective: The purpose of this study was to evaluate whether loss of consciousness (LOC), retrograde amnesia (RA), and anterograde amnesia (AA) independently influence a particular aspect of post-concussion cognitive functioning—across-test intra-individual variability (IIV), or cognitive dispersion. Method: Concussed athletes (N = 111) were evaluated, on average, 6.04 days post-injury (SD = 5.90; Mdn = 4 days; Range = 1–26 days) via clinical interview and neuropsychological assessment. Primary outcomes of interest included two measures of IIV—an intra-individual standard deviation (ISD) score and a maximum discrepancy (MD) score—computed from 18 norm-referenced variables. Results: Analyses of covariance (ANCOVAs) adjusting for time since injury and sex revealed a significant effect of LOC on the ISD (p = .018, η p 2 = .051) and MD (p = .034, η p 2 = .041) 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 AA (all p > .05). Conclusions: LOC, but not RA or AA, was associated with greater variability, or inconsistencies, in cognitive performance acutely following concussion. Though future studies are needed to verify the clinical significance of these findings, our results suggest that LOC may contribute to post-concussion cognitive dysfunction and may be a risk factor for less efficient cognitive functioning.

Validity of postconcussion only algorithms in collegiate athletes following sports-related concussion.

“…Two measures of IIV were calculated: (1) an Intra-Individual Standard Deviation (ISD) score; and (2) a Maximum Discrepancy (MD), or range, score. Per Merritt, Rabinowitz, et al (2018, 2020), the scores were calculated as follows: 1) ISD = the standard deviation of the standard scores across all 17 neuropsychological indices; and 2) MD = the difference between each athlete’s lowest and highest cognitive test score across these indices. Higher scores represented greater IIV, or inconsistency of performance, for both IIV indices.…”

“…Primary Hypothesis 1: Compared with the Recovered groups, the Not Recovered groups will show significantly higher Immediate Post- Primary Hypothesis 2: Compared with the Recovered groups, the Not Recovered groups will show significantly greater cognitive variability, as reflected in two measures of intraindividual variability (IIV), across the 17 cognitive indices included as part of the algorithm postconcussion. Prior work has shown that athletes show increased cognitive variability postinjury compared with nonconcussed athletes (Merritt et al, 2020;Merritt, Ukueberuwa, et al, 2018;Rabinowitz & Arnett, 2013), suggesting that cognitive variability can be a useful indicator of outcome that goes beyond mean score differences or a simple count of impairments.…”

Test-Retest Reliability of Immersive Virtual Reality Measures of Perceptual-Motor Performance

“…Numerous studies have documented an inverse relationship between behavioral performance consistency and moment-to-moment brain signal variability (Fjell et al, 2011;Garrett et al, 2014Garrett et al, , 2020Grady & Garrett, 2018;Johnson et al, 2015;Kelly et al, 2008;McIntosh et al, 2008;Mennes et al, 2011;Roberts et al, 2022;Wang et al, 2017). Furthermore, elevated IIV has been associated with a history of sport-related concussion (McGowan et al, 2018(McGowan et al, , 2019Merritt et al, 2019Merritt et al, , 2021Parks et al, 2015;Rabinowitz & Arnett, 2013;Wong et al, 2023). Despite growing evidence that longitudinal assessment of RT-related measures (e.g., RCS and IIV) may serve as important indicators of subtle change in brain processing efficiency, assessment of distribution normality and test-retest reliability have received relatively little attention.…”

Dispersion of cognitive performance test scores on the MATRICS Consensus Cognitive Battery: A different perspective

“…One of the limitations of using a composite score as the unit of measurement that is compared across treatment sessions is that this approach does not account for changes in the variability of performances within a single testing session. The study of intra-individual variability (IIV) typically takes one of two forms: (1) inconsistency, or variability among responses within a reaction-time task, or (2) dispersion, or variability among test performances (relative to applicable norms) within a single neurocognitive battery ( Cole et al, 2011 ; Hill et al, 2013 ; Merritt et al, 2021 ; Vance et al, 2021 ).…”

“…The dispersion of performance within a neurocognitive battery has proven to be a valuable metric for a variety of therapeutic states. Greater dispersion within single-session test batteries relative to matched controls has been demonstrated in individuals with bipolar disorder ( Depp et al, 2012 ), HIV infection ( Hines et al, 2016 ; Vance et al, 2021 ), hepatitis C virus infection ( Morgan et al, 2012 ), West Nile virus infection ( Sheppard et al, 2018 ), veterans with mild traumatic brain injury ( Merritt et al, 2018 ; Sorg et al, 2020 ), athletes with loss of consciousness secondary to concussion ( Merritt et al, 2021 ), increased risk of progression to Alzheimer's disease ( Halliday et al, 2018 ), and greater severity of traumatic brain injury ( Hill et al, 2013 ). In many of these investigations, the sensitivity of dispersion to deficits appears to be independent of mean level of cognitive performance ( Cole et al, 2011 ; Hines et al, 2016 ; MacDonald et al, 2006 ; Reichenberg et al, 2006b ).…”