Abstract
Background: Concussion is an injury that commonly occurs in the collision sports such as rugby union, rugby league and American football. A player suspected of a concussive brain injury is usually assessed using a multifaceted approach utilising both subjective and objective approaches. The subjective approaches include the self-report of symptoms and structured questions, while objective methods include balance and neuropsychological tests. Currently, the common practice is to obtain the individualised self-reported symptoms during a pre-season baseline testing phase to compare those reported following a suspected concussion. This practice is followed in order to inform the diagnosis of a concussive injury and to assist in decision-making on when the player should return-to-play (RTP).
However, the presence of ‘post concussion-like symptoms’ is also reported in normal (non-concussed) healthy individuals. Additionally, there is also a possibility of several factors (e.g. stress, depression) that can influence the symptom reporting. The impact of these variables on symptom reporting is not well understood, and generally not accounted for in current practice. Furthermore, the influence of gender and key (selected) parameters of exercise on symptom reporting following participation in exercise/sports requires further investigation. In the majority of literature reporting on concussion symptomatology, the symptom data are collected in a structured/prescribed format. Questions arise as to whether these data accurately reflect the symptom reporting status of an individual.
Thesis Aim: The overall aim of this thesis was to explore the factors that influence the reporting of post concussion-like symptoms during daily life activities and following exercise/sports participation in a cohort of university students.
Methods: A series of four related studies was conducted to explore the potential factors that could have an impact on symptom reporting (using the SCAT2 post-concussion symptom scale) at rest and also after participation in exercise/sport. A cross-sectional web-based survey (Study 1) was undertaken, which included 603 (154 males & 449 females) participants who reported their symptoms and other constructs (e.g. anxiety, mental fatigue) as a one-time measure in the real-world (non-clincial or non-laboratory). Subsequently, a longitudinal study (Study 2) employed an experience sampling methodology, where 110 participants reported their symptoms and other constructs such as stress and physical fatigue when prompted (text message) at pre-determined times for 7 consecutive days.
A systematic narrative review (Study 3) was conducted to investigate the symptom response following acute bouts of exercise, and to identify the key exercise parameters which could have an influence on symptom reporting. Following this, a pre-post observational study (Study 4) was conducted with 260 (146 males & 114 females) participants to investigate the potential influence of key exercise parameters on the reporting of symptoms after a period of exercise/sports participation of the participant’s choice.
Results: The results of the cross-sectional web-based survey (Study 1) found that the reporting of post concussion-like symptoms is influenced by a range of both psychological (e.g. stress) and lifestyle (e.g. alcohol consumption) factors. For example, multiple linear regression modelling found that there was a 2.75 unit increase in the total symptom score (TSS) for those participants who endorsed having consumed alcohol in the last 24 hours. Two pairs of predictor variables also showed a significant interaction effect, which was further explored by plotting the simple slopes to enhance the interpretation of data.
Of the 110 participants who participated in the longitudinal study (Study 2), 19% of them showed a decreasing trend in the post concussion-like symptoms reported over the 7 days. Additionally, linear mixed-effects analyses revealed that the location of the participant at the time of reporting, physical fatigue (p<.001) and mental fatigue (p<.001) had an influence on the change in post concussion-like symptoms (TSS) reported over the 7 days. In the post-hoc results of the predictor variable, the location of the participant showed that participants reported increased symptoms when they were at university compared to a flat/college (p<.05).
The systematic narrative review (Study 3) identified five studies, which have been conducted in controlled conditions, each study with varying objectives. In general, the overall results suggest that an acute bout of exercise lasting for 15 minutes tends to provoke and increase symptoms with their return to baseline levels after a period of 5 minutes rest. The pre-post observational study (Study 4) demonstrated that only the variable of gender had an impact on symptom reporting. Specifically, there was a 4.03 unit decreased (improved) change in the TSS for females compared to males. The main effect of the predictor variable of the volume of exercise was non-significant; however, there was a significant interaction effect (p<.05) with the predictor variable of gender.
Conclusion: Clinicians need to exercise caution when interpreting the symptom scores during baseline testing and subsequent assessments. This is suggested as there are a number of potential psychological and lifestyle factors that have been shown to influence the reporting of post concussion-like symptoms and these need to be accounted for when interpreting the symptom scores. In addition, health professionals (e.g. sports physiotherapists) associated with concussion assessment and management must be aware that the symptoms reported over time are likely to have an inherent variation. This awareness is required as it can lead to erroneous interpretation of the symptom scores, when serial assessments are conducted to monitor recovery in order to make decisions on RTP. Currently, none of the key exercise parameters (e.g. intensity) were shown to impact symptom reporting. However, study findings have indicated that females report symptoms differently compared to males. Therefore, gender needs to be considered when an assessment is carried out following participation in exercise/sports.