Peer-Reviewed Articles

Published articles speak to the validity and reliability of the Axon Sports CCAT

Computerised cognitive assessment of athletes with sports related head injury.
Author(s):
Collie, Darby & Maruff
Year:
2001
Published In:
Br J of Sports Med, 35(5), 279-302
Type:
Review
Status:
Published
Abstract:
Professional and amateur participants in many sports are at risk of brain injury caused by impact with other players or objects. In many cases, mild cognitive deficits may persist after the common neurological signs of brain injury have passed. In recent years, the athlete's cognitive status after concussion has been measured with conventional "paper and pencil" neuropsychological tests. However, such tests are not ideal for sporting settings, as they are designed for the detection of gross cognitive impairments at a single assessment, not for the identification of mild cognitive deficits on repeated assessment. A number of computerised cognitive assessment tests and test batteries have been developed over the past two decades. These batteries offer major scientific and practical advantages over conventional neuropsychological tests which make them ideal for the assessment of cognitive function in sportspeople. This review first describes the problems associated with cognitive assessment of people with sports related cognitive deficits, and then critically examines the utility of conventional neuropsychological and computerised cognitive tests in sporting settings.
Cognition in the days following concussion. Comparison of symptomatic vs asymptomatic athletes.
Author(s):
Collie, Makdissi & Maruff
Year:
2006
Published In:
Journal of Neurology, Neurosurgery & Psychiatry
Type:
Article
Status:
Published
Abstract:
Background: Concussion is a common neurological injury occurring during contact sport. Current guidelines recommend that no athlete should return to play while symptomatic or displaying cognitive dysfunction. This study compared post-concussion cognitive function in recently concussed athletes who were symptomatic/asymptomatic at the time of assessment with that of non-injured (control) athletes. Methods: Prospective study of 615 male Australian Rules footballers. Before the season, all participants (while healthy) completed a battery of baseline computerised (CogSport) and paper and pencil cognitive tasks. Sixty one injured athletes (symptomatic = 25 and asymptomatic = 36) were reassessed within 11 days of being concussed; 84 controls were also reassessed. The serial cognitive function of the three groups was compared using analysis of variance. Results: The performance of the symptomatic group declined at the post-concussion assessment on computerised tests of simple, choice, and complex reaction times compared with the asymptomatic and control groups. The magnitude of changes was large according to conventional statistical criteria. On paper and pencil tests, the symptomatic group displayed no change at reassessment, whereas large improvements were seen in the other two groups. Conclusion: Injured athletes experiencing symptoms of concussion displayed impaired motor function and attention, although their learning and memory were preserved. These athletes displayed no change in performance on paper and pencil tests in contrast with the improvement observed in symptomatic and non-injured athletes. Athletes experiencing symptoms of concussion should be withheld from training and competition until both symptoms and cognitive dysfunction have resolved.
Practice effects associated with the repeated assessment of cognitive function using the CogState battery at 10-minute, one week and one-month test retest intervals.
Author(s):
Falleti, Maruff, Collie & Darby
Year:
2006
Published In:
Journal of Clinical and Experimental Neuropsychology 28, 1095-1112
Type:
Article
Status:
Published
Abstract:
There are many situations in which cognitive tests need to be administered on more than two occasions and at very brief test-retest intervals to detect change in group performance. However, previous literature has not specifically addressed these important issues. The main aim of the current study was to examine these two factors by using a computerized cognitive battery designed specifically for the repeated assessment of cognition (i.e., CogState) in healthy young adult individuals. A further aim of the study was to examine how many times the battery needed to be completed before performance, as measured by the battery, stabilized. Forty-five adults (Age range: 18 - 40 years) completed the battery four times at ten-minute test-retest intervals, a fifth time at an interval of one week. The results illustrated that when brief test-retest intervals were used (i.e., 10 minutes), performance stabilized after the second assessment, as significant practice effects were generally observed between the first and the second assessments. Practice effects were also observed on some of the tasks at a one-week test-retest interval. Due to these findings, fifty-five adults (Age range: 18 - 40 years) completed the battery twice at ten-minute test-retest intervals (i.e., to eliminate the initial practice effect), and a third time at an interval of one month. No practice effects were observed. The implications of the results are discussed in terms of methods that can be adopted in order to minimize practice effects when this particular cognitive battery is used.
A prospective controlled study of cognitive function during an amateur boxing tournament.
Author(s):
Moriarity, Collie, Olson, Buchanan, Leary, McStephen & McCrory
Year:
2004
Published In:
Neurology, 62, 1497-1502
Type:
Article
Status:
Published
Abstract:
Background: Few studies have reported acute postbout cognitive function in amateur boxers, and none have documented the effects of repeated boxing bouts within a short time frame. Objective: To determine whether participation in a 7-day amateur boxing tournament is associated with acute deterioration in cognitive test performance. Methods: A prospective study was done of 82 collegiate amateur boxers participating in a 7-day single elimination tournament and a group of 30 matched nonboxing control participants. No participants had a history of recent concussion or past history of brain injury. For boxers, cognitive assessment using a computerized test battery was performed before the tournament and within 2 hours of completing each bout. Tests of simple and choice reaction time, working memory, and learning were administered. Analysis of variance was conducted to compare the serial performance of control participants with that of boxers participating in one, two, and three bouts. Results: The 82 boxers fought 159 times. Cognitive testing was performed after 142 of these bouts. On simple reaction time, choice reaction time, and working memory tasks, the serial performance of boxers participating in three bouts (n _ 22) was equivalent to that of boxers participating in two bouts (n _ 22) and one bout (n _ 32) and to nonboxing control participants (n _ 30). An improvement in performance was observed on the learning task in boxers participating in three bouts. Boxers whose bout was stopped by the referee (n _ 7) displayed significant slowing in simple and choice reaction time. Conclusions: With the exception of boxers whose contest is stopped by the referee, amateur boxers participating in multiple bouts during a 7-day tournament display no evidence of cognitive dysfunction in the immediate postbout period.
Natural History of Concussion in Sport Markers of Severity and Implications for Management
Author(s):
Makdissi, Darby, Maruff, Ugoni, Brukner & McCrory
Year:
2010
Published In:
The American Journal of Sports Medicine, Vol. 38, No. 3
Type:
Article
Status:
Published
Abstract:
Background: Evidence-based clinical data are required for safe return to play after concussion in sport. Purpose: The objective of this study was to describe the natural history of concussion in sport and identify clinical features associated with more severe concussive injury, using return-to-sport decisions as a surrogate measure of injury severity. Methods: Male elite senior, elite junior, and community-based Australian Rules football players had preseason baseline cognitive testing (Digit Symbol Substitution Test, Trail-Making Test–Part B, and CogSport computerized test battery). Players were recruited into the study after a concussive injury sustained while playing football. Concussed players were tested serially until all clinical features of their injury had resolved. Results: Of 1015 players, 88 concussions were observed in 78 players. Concussion-associated symptoms lasted an average of 48.6 hours (95% confidence interval, 39.5-57.7 hours) with delayed return to sport correlated with _4 symptoms, headache lasting _60 hours, or self-reported ‘‘fatigue/fogginess.’’ Cognitive deficits using the Digit Symbol Substitution Test and Trail-Making Test–part B recovered concomitantly with symptoms, but computerized test results recovered 2 to 3 days later and remained impaired in 35% of concussed players after symptom resolution. Conclusion: Delayed return to sport was associated with initially greater symptom load, prolonged headache, or subjective concentration deficits. Cognitive testing recovery varied, taking 2 to 3 days longer for computerized tests, suggesting greater sensitivity to impairment. Therefore, symptom assessment alone may be predictive of but may underestimate time to complete recovery, which may be better estimated with computerized cognitive testing.
Qualitative similarities in cognitive impairment associated with 24h of sustained wakefulness and a blood alcohol concentration of 0.05%.
Author(s):
Falleti, Maruff, Collie, Darby & McStephen
Year:
2003
Published In:
J Sleep Res, 12, 265-74
Type:
Article
Status:
Published
Abstract:
Previous studies that have quantified fatigue-related cognitive impairment as blood alcohol concentration (BAC) equivalents have been limited by two issues: the effect of practice on tests of cognition and, more importantly, the statistic used to quantify change in cognitive performance. The current study addressed these issues by adopting an ABACA design, which allowed for the adequate control of practice effects, and by using effect size metrics, which enabled direct comparisons to be made in performance impairments as a result of fatigue (i.e. sustained wakefulness of 24 h) and alcohol (i.e. BAC of 0.05%). Cognitive performance under the fatigue and alcohol conditions required the use of the CogStateTM battery. It was demonstrated that fatigue caused greater impairment than alcohol on the speed of continuous attention and memory and learning, and on the accuracy of complex matching. Alcohol was more detrimental than fatigue only on the accuracy of memory and learning. Performances on the remaining tasks were the same for both the fatigue and alcohol conditions. These differences and similarities in performance impairment are discussed emphasizing the deleterious cognitive effects of relatively short periods of sustained wakefulness.
CogSport: Reliability and correlation with conventional cognitive tests used in post-concussion medical examinations.
Author(s):
Collie, Maruff, Makdissi, McCrory, McStephen & Darby
Year:
2003
Published In:
Clinical Journal of Sport Medicine, 13, 28-32
Type:
Article
Status:
Published
Abstract:
Objective: To determine the repeatability and of a computerized cognitive test designed to monitor recovery from concussion and assist team physicians make return to play decisions (CogSport™). To determine the correlation between CogSport and two conventional neuropsychological tests. Design: Prospective, serial investigation of cognitive function. Setting: Professional and semi-professional Australian Football clubs and a university affiliated research institute in Melbourne, Australia. Participants: Three-hundred healthy young adults, including 240 elite athletes. Main Outcome Measures: Intra-class correlation (ICC) coefficients for CogSport performance measures administered serially. ICC between CogSport performance measures and conventional neuropsychological tests. Normative data for CogSport performance measures. Results: Measures of psychomotor function, decision making, working memory and learning were highly reliable. Some measures also displayed high correlations with conventional neuropsychological tests of information processing and attention. Preliminary normative data is described. Conclusions: CogSport is a highly reliable cognitive function test when administered to healthy young adults and elite athletes. CogSport measures similar cognitive functions as conventional tests used commonly in concussion research.
Cognitive testing in early-phase clinical trials: Development of a rapid computerized test battery and application in a simulated Phase I study.
Author(s):
Collie, Darekar, Weissgerber, Toh, Snyder, Maruff & Huggins
Year:
2007
Published In:
Contemporary Clinical Trials 28 (2007) 391–400
Type:
Article
Status:
Published
Abstract:
Background: Inclusion of cognitive assessment in Phase I trials of novel pharmaceutical agents may help identify subtle yet meaningful CNS effects early in clinical development, and lead to a greater understanding of the pharmacokinetic/ pharmacodynamic relationship prior to entering pivotal late-phase trials. Aims: To examine issues surrounding the inclusion of a computerised cognitive test battery in Phase I clinical trials. Methods: A 12-minute battery of five computerized cognitive tasks was administered to 28 healthy males in a double-blind, single ascending dose study using three doses of midazolam (0.6 mg, 1.75 mg and 5.25 mg) with placebo insertion. Subjects were enrolled and assessed at two Phase I units. Statistical analyses sought to determine the sensitivity of the test battery to sedation related cognitive dysfunction, any between-site differences in outcome, and also the effects of repeated test administration (i.e., practice or learning effects). Results: There were no significant differences in data collected between sites. All standard safety measurements were completed. No substantial technical issues were noted. No learning effects were observed on four of the five cognitive tasks. ANOVA comparing baseline to post-baseline results revealed significant cognitive deterioration on all five cognitive tasks 1 h following administration of 5.25 mg midazolam. The magnitude of these changes were very large according to conventional statistical criteria. Smaller but significant changes were observed on a subset of memory and learning tasks at 1 h post-dosing in 1.75 mg condition, and at 2 h post-dosing in the 5.25 mg condition. Conclusions: The cognitive test battery was well tolerated by subjects and research unit staff. The tests demonstrated minimal learning effects, were unaffected by language and cultural differences between sites, and were sensitive to the sedative effects of midazolam. Inclusion of this cognitive test battery in future studies may allow identification of cognitive impairment or enhancement early in the clinical development cycle.
The assessment of cognitive function in advanced HIV-infection and AIDS Dementia Complex using a new computerised cognitive test battery.
Author(s):
Cysique, Maruff, Darby & Brew
Year:
2006
Published In:
Archives of Clinical Neuropsychology
Type:
Article
Status:
Published
Abstract:
The validity of a new computerised battery called CogState was determined in 60 individuals with advanced human immunodeficiency virus-1 (HIV-1) infection from which eleven were assessed as AIDS dementia complex (ADC) stage 1 or 2. Twenty-one seronegative individuals were recruited as controls. Participants were evaluated with a brief computerised examination, lasting 10–15 min, assessing reaction time, accuracy in working memory and learning. They were also assessed with a standard neuropsychological examination lasting 1 h 30 min on average. The computerised assessment demonstrated a good sensitivity of 81.1% and specificity of 69.9% as well as good positive predictive value (81%) and acceptable construct validity (.45–.62). Slowed reaction time and learning deficits in the computerised battery were characteristic of ADC. This study supports the utility of a brief computerised battery in the detection of HIV-associated neurocognitive impairment that could be used for wide-scale screening.
Fatigue-related impairment in the speed, accuracy and variability of psychomotor performance: comparison with blood alcohol levels.
Author(s):
Maruff, Falleti, Collie, Darby & McStephen
Year:
2005
Published In:
J Sleep Res; 14(1), 21-7
Type:
Article
Status:
Published
Abstract:
Cognitive performance is impaired by fatigue arising from sustained wakefulness and alcohol. Three recent papers directly compared the effects of increasing fatigue and blood alcohol concentration (%BAC) to provide a framework for understanding fatigue-related cognitive impairment. While the expression of fatigue-related cognitive impairments in terms of %BAC equivalents is sound, the methodology in each study was flawed in that the statistics used to compare the effects of %BAC and fatigue on cognition did not account for variation between or within each condition. The point estimates of the difference between a baseline and any level of fatigue or %BAC provided no indication of the size of difference that could reasonably be expected by chance. Importantly, all studies showed that variation increased as cognitive performance declined because of both increasing fatigue and %BAC. The current study compared the effect of increasing levels of %BAC and fatigue on the simple reaction task from the CogState test battery on 40 healthy adults using statistical methods that account for intra-individual and within-group variability in performance. After 24 h of sustained wakefulness and with 0.08%BAC, individuals showed maximal cognitive impairment; however, the magnitude of impairment found for fatigue was equivalent only to that observed for 0.05%BAC. Re-analysis of the data using percentage change scores indicated that the magnitude of fatigue-related cognitive impairment was much greater than that detected for 0.08%BAC. This suggests that previous studies that have not accounted for variability in the performance data have overestimated the effect of fatigue on cognitive performance.
Validity of the CogState Brief Battery: Relationship to Standardized Tests and Sensitivity to Cognitive Impairment in Mild Traumatic Brain Injury, Schizophrenia, and AIDS Dementia Complex
Author(s):
Maruff , Thomas, Cysiqued, Brewe, Collie, Snyder, Pietrzak
Year:
2009
Published In:
Arch Clin Neuropsychol 2009;24:165-178
Type:
Publication
Status:
Published
Abstract:
This study examined the validity of the four standard psychological paradigms that have been operationally defined within the CogState brief computerized cognitive assessment battery. Construct validity was determined in a large group of healthy adults. CogState measures of processing speed, attention, working memory, and learning showed strong correlations with conventional neuropsychological measures of these same constructs (r’s ¼ .49 to .83). Criterion validity was determined by examining patterns of performance on the CogState tasks in groups of individuals with mild head injury, schizophrenia, and AIDS dementia complex. Each of these groups was impaired on the CogState performance measures (Cohen’s d’s ¼ 2.60 to 21.80) and the magnitude and nature of this impairment was qualitatively and quantitatively similar in each group. Taken together, the results suggest that the cognitive paradigms operationally defined in the CogState brief battery have acceptable construct and criterion validity in a neuropsychological context.
Do minor head impacts in soccer cause concussive injury? A prospective case-control study
Author(s):
Straume- Næsheim, Andersen, Holme, McIntosh, Dvorak and Bahr
Year:
2009
Published In:
Congress of Neurological Surgeons - Neurosurgery 64:719–725, 2009
Type:
Publication
Status:
Published
Abstract:
OBJECTIVE: Our objective was to determine whether minor head trauma in elite soccer matches causes measurable impairment in brain function. METHODS: Baseline neuropsychological testing was completed by professional soccer players in the Norwegian elite league, Tippeligaen, before the 2004 and 2005 seasons (n 462). A player who experienced a head impact during a league match completed a follow- up test the next day (head impact group). Videotapes of all impacts were collected and reviewed. A group of players without head impacts was also tested after a league match to serve as controls (matched control group; n 47). RESULTS: A total of 228 impacts were identified, and 44 (19.3%) of these were followed up with a CogSport test (CogState, Ltd., Charlton South, Australia; the players who were tested tended to have more severe injuries, but there were only 6 cases with loss of consciousness). The head impact group had a greater change in reaction time from baseline to follow- up compared with the matched control group with regard to the 3 simplest tasks. The largest deficits were seen among the players reporting acute symptoms after the impact, but deficits were also demonstrated among asymptomatic players. Players who experienced 1 or more head impacts during the 2004 season showed a reduction in neuropsychological performance when tested before the 2005 season. However, none of these players was impaired when compared with the test manufacturer’s normative data. CONCLUSION: A reduced neuropsychological performance was found after minor head impacts in soccer, even in allegedly asymptomatic players. However, the longterm cognitive consequences are uncertain.
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