Sustaining a concussion is a significant risk for athletes who regularly participate in contact sports such as football or rugby. Epidemiological evidence suggests that adolescent athletes may be at risk of more frequent and more severe concussive injuries than adults. Yet what we know about the impact of sports-related concussion on brain function is predominantly derived from studies of adult athletes concussed whilst participating in college or professional-level competitions.
This thesis replicates and extends previous research by investigating the neuropsychological effect of concussion in adolescent athletes. Four key questions were addressed: does the impact of concussion on athletes’ neurocognitive, symptomatic and postural functioning differ between adolescents and adults, what are the key modifiers of these injury outcomes, which psychometric instruments offer the most sensitive assessment of sports-related concussion, and what is the acute effect and the natural course of recovery from a single recent concussion in adolescent athletes. The results of this program of research will inform the evidence-based assessment and management of concussion specific to young athletes.
First, a series of three meta-analytic studies were conducted (Studies 1 to 3). Ninety-two independent samples of sports-related concussion were retrieved from the published literature (January 1970 to August 2011) and subjected to in-depth meta-analytic review. This was in order to quantify the state of the art and to identify the remaining gaps in our empirical knowledge. Extensive data extraction included variables pertaining to research design and methodology, sample and injury characteristics, the timing and method of post-injury assessment, and variables specific to the meta-analytic techniques used. Outcomes of interest were concussed athletes’ (n = 3,811) performance on neuropsychological tests, self-report symptom severity scales (total scores), and measures of postural stability, as compared to their pre-injury baseline and/or an uninjured control group (n = 5,641). Study 1 quantified the magnitude of the effect of sports-related concussion onneuropsychological, symptomatic, and postural functioning, and examined which pre-existing athlete characteristics moderate this effect. Study 2 examined which injury characteristics are predictive of worse post-concussion neuropsychological deficits in adolescent and adult athletes. Study 3 delineated the psychometric instruments commonly used to assess sports-related concussion sequelae in adolescent and adult athletes, and derived evidence-based recommendations for the selection of sensitive outcome measures.
The findings of this meta-analytic series were then applied to the prospective assessment of a clinical sample of young Australian athletes at risk of concussion (Study 4). Ninety-five participants were recruited from high school rugby and Under 18’s Australian Rules football teams. All participants were assessed twice preseason using an evidence-based battery of neuropsychological, symptom severity, and postural stability outcome measures. Three athletes who were subsequently
concussed during play were reassessed within 48 hours of injury, and again at 1 week, 1 month and 3 months post-injury. Fifteen matched uninjured controls were also reassessed at these intervals. Follow-up intervals were selected for consistency with documented neurometabolic recovery periods, and with the follow-up intervals typically reported within the extant empirical literature. Concussed and control participants’ baseline (premorbid) neurocognitive test performance, as well as the rate of change in their performance upon retest, were compared. Reliable change indices were calculated from concussed and control athletes’ retest performance, in order to quantify the acute effect of concussion and to identify when criteria for recovery from injury had been satisfied. Recovery was defined as a concussed athlete’s return to practiced preseason performance after controlling for measurement error and the attenuating effect of repeat assessment (derived from control group retest data). Clinically useful psychometric data (test-retest reliabilities, mean difference scores, and estimates of sample variance) were also reported.
In summary, the findings of this program of research demonstrate that the neuropsychological sequelae of concussion (Studies 1, 2 and 3) and the optimal means with which to measure postconcussion impairment and recovery (Studies 1 and 3) differ between adolescent and adult athletes. Adolescent athletes experience greater neuropsychological impairment than adults within the first 10 days post-injury (Studies 1, 2 and 3), and some individuals may take up to 30 days, and in some instances 90 days, to return to a practiced pre-injury level of functioning (Study 4). This research project also demonstrates that postural stability measures, in addition to neuropsychological tests and self-report symptom severity scales, are an important component of an optimised evidencebased protocol for the prospective assessment of sports-related concussion (Studies 3 and 4). While further research is yet needed to replicate these results, a conservative and individualised approach is recommended for the management of concussive injury in adolescent athletes, particularly within the first 10 days of injury when return-to-participation decision-making typically occurs. This is particularly so in the presence of key modifiers of injury such as a loss of consciousness, posttraumatic amnesia, post-concussion symptoms or recent previous concussion (Study 2). A graduated progression of return-to-participation in contact sports should commence only after all post-concussion sequelae have resolved. Specifically, it is recommended that, in addition to theresolution of post-concussion symptoms, resolution of neurocognitive and postural functioning should be attained before return-to-participation protocols are commenced. Moreover, education of adolescent athletes, their parents and their coaches regarding the potentially greater risk of adverse outcomes from concussion in adolescent athletes, and hence the need for adolescent-specific guidelines for injury management and safe return-to-play, is also recommended.