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What is known about the topic?

Little is known about the impact of sports injury compared to non-sports injury, on mild Traumatic Brain Injuries (TBI) recovery.

What did this study ask?

To compare post-concussion symptoms in patients who sustained a sports-related mild TBI to those with non-sports-related mild TBI.

What did this study find?

Patients who sustained sports-related-mild TBI are at lower risk of experiencing symptoms such as fatigue and dizziness 90 days post-injury.

Why does this study matter to clinicians?

Clinicians should be mindful that non-sports-related-mild TBI patients may experience more post-concussion symptoms and physical activity level may influence rehabilitation.

Introduction

In 2013, traumatic brain injuries (TBI) led to approximately 2.8 million emergency department (ED) visits, hospitalizations and deaths in United States [1]. Mild TBI, or concussion, is the most common type of TBI [2] and must, therefore, be considered a serious public health issue. One Canadian study estimated that the incidence of hospital-treated mild TBI in Ontario was at least 493 per 100,000 patients [3]. Although this type of trauma can be the result of a wide variety of mechanisms, 54% are sport-related in patients aged 16–34 years according to The Canadian National Health Population Survey [4]. Sports-related mild TBI are defined in the literature as a mild TBI that was induced by biomechanical forces during recreational or high-level sports practice [5]. It is estimated that 1.6–3.8 million sports-related TBI (which includes mild TBI) occur each year in the United States [6].

There are numerous available studies regarding mild TBI pathophysiology [7], diagnosis [5, 8], treatments [5, 9, 10], predictors of wellness [11, 12] and symptom evolution [13]. Since about 24% of mild TBI patients remain significantly impaired by persistent symptoms such as headaches, dizziness and fatigue at 3-month follow-up [14], many studies have analyzed the impact of mechanisms of injury on persistent post-concussion symptoms while evaluating other risk factors [11, 15,16,17,18]. However, sport as the mechanism of injury has an impact on the recovery and return to normal activities.

Only a few studies have attempted to compare the recovery of patients who sustained a sports-related mild TBI with the recovery of patients who sustained other types of injuries [11, 19]. However, most of these studies have focused on high school athletes [19, 20], elite collegiate athletes [21, 22] or professional athletes [23, 24]. Understanding the evolution of symptoms depending on the initial mechanism may help to predict recovery or capture particular evolution patterns. The main objective of this study is to compare post-concussion symptoms in patients who sustained a sports-related mild TBI to those who sustained non-sports-related mild TBI at 7 and 90 days post-mild TBI. Secondary objectives are to compare the prevalence of each Rivermead Post-concussion questionnaire symptom (score of ≥ 2), individually assessed, the prevalence of a total Rivermead Post-concussion questionnaire score ≥ 21 points (a potential cutoff score), and the prevalence of patients who returned to their normal daily activities at 7 and 90 days post-mild TBI.

Methods

Study design and setting

This is a secondary analysis of a multicentre prospective cohort study, which was conducted in seven Canadian Emergency Departments (ED) (five level I trauma centers: the CHU de Québec—Université Laval (Hôpital de l’Enfant-Jésus), the Hôpital du Sacré-Coeur de Montréal, The Ottawa Hospital, Sunnybrook Health Sciences Center (Toronto), Foothills Medical Center (Calgary), one level II trauma center: CISSS de Chaudière-Appalaches and one academic non-trauma center: CHU de Québec—Université Laval (CHUL)), between 04/07/2010 and 30/09/2018. Each research assistant received extensive standardized training to ensure the quality of data collection, which included a group session and personalized field training with supervision by the study coordinator for the study duration.

Population

Emergency physicians and research assistants identified potential participants in the ED. Patients were included if they: (1) had a documented mild TBI (defined as a Glasgow Coma Scale (GCS) score between 13 and 15 at 30 min post-injury, and one or more of the following symptoms: loss of consciousness (< 30 min), post-traumatic amnesia (< 24 h), impaired mental state at time of accident (confusion, disorientation and/or transient neurological deficit) [25], (2) had their mild TBI within 24 h of their ED visit and (3) were aged ≥ 14 years. Patients who were hospitalized following their ED visit, who were unable to consent or unable to speak French or English were excluded.

Data collection

Once informed consent was obtained, clinical and sociodemographic data were also collected. Additional information regarding injury mechanism (i.e. motor vehicle collision, assault, and sports), associated injuries, previous hospitalizations, previous head traumas and history of psychiatric disorders was also collected. Three follow-up phone interviews were conducted by a research assistant at 7, 30 and 90 days post-injury. Each of the follow-ups included a question regarding patients’ ability to return to each of their usual daily activities (e.g., work, studying, and reading) due to post-concussion symptoms. The replies to the question were coded into a dichotomous variable (“yes” or “no”). The Rivermead Post Concussion Symptoms Questionnaire [26,27,28], a validated 64-point test commonly used by health-care professionals to assess post-concussion symptoms, was also administered during those phone interviews to the study participants. This test requires patients to rate the severity of 16 symptoms (affective, physical and cognitive) using a scale ranging from 0 to 4 (0: absent, 1: same as before, 2: mild, 3: moderate, and 4: severe), compared to their pre-injury status. Thus, a score ≥ 2 was considered to be consistent with a mild TBI-related problem [26,27,28]. A high Rivermead Post-concussion questionnaire score indicates a higher number and greater severity of symptoms.

Outcome measures

To describe and compare the evolution of post-concussion symptoms between patients who sustained sports-related mild TBI and those who sustained non-sports-related mild TBI, the main outcome was defined by the presence of three symptoms or more on the Rivermead Post-concussion questionnaire at 90 days post-injury. This definition is based on the criteria of The International Classification of Diseases, 10th revision (ICD-10) [29]. The secondary outcomes which were all evaluated at 7 and 90 days post-injury were: (1) the prevalence of each symptom of the Rivermead Post-concussion questionnaire, individually assessed, (2) a total score of 21 points or more on the Rivermead Post-concussion questionnaire, a potential cutoff score determined by the study steering committee since none exist in the literature, and (3) the patient’s ability to return to their normal daily activities due to post-concussion symptoms, as assessed by patients themselves.

Data analyses

Descriptive analyses were used for sociodemographic variables. Measured outcomes were computed and compared between the two groups of patients (sports-related mild TBI and non-sports-related mild TBI) using Chi-square tests for normally distributed data and the Fisher’s exact test was used for non-normal data. Continuous variables were compared using Student’s T tests when the distribution was normal, and the Wilcoxon test was used for non-normal distribution.

A Generalized Poisson Distribution estimating equations (GEEs) regression model with robust standard errors was applied to evaluate the difference of symptoms between the two groups at 7 days, 30 days and 90 days post-injury. For relative risk (RR) calculation, multiple comparison adjustments for confidence intervals and p values were used by employing Tukey–Kramer method. The following potentially confounding factors were used to adjust relative risks of post-concussion symptoms: age category (14–24, 25–34, 35–44, 45–54, 55–64, ≥ 65 years), previous TBI, presence of previous psychiatric disorders, prescribed medication, presence of concomitant injuries and headache. These three last covariates were also used to adjust the relative risks of the impact of mechanism of injury on patients’ normal daily activities. Lastly, Inverse Probability-of-Censoring Weights were used to correct for selection bias due to loss to follow-up at 7, 30 and 90 days [30]. All analyses were performed using the Statistical Analysis System (SAS Institute, Inc., Cary, NC, version 9.4).

This study was approved by the Research Ethics Board of the CHU de Québec—Université Laval.

Results

A total of 1727 patients were included in this study. Table 1 shows the sociodemographic and clinical characteristics of our study population. Three hundred and sixty-three patients (21.0%) sustained a sports-related mild TBI. Both groups had similar gender distribution. Median age was lower for the sports-related mild TBI group. Sports-related mild TBI patients differed significantly from the non-sports-related mild TBI patients in regard to the presence of previous psychiatric disorders, previous TBI, at least one prescribed medication and isolated mild TBI (versus mild TBI with associated injuries). There were also some differences regarding both groups’ initial symptoms at time of arrival in the ED. The sports-related mild TBI group differed significantly from the non-sports-related mild TBI cohort in terms of headaches, confusion and loss of consciousness.

Table 1 Clinical and sociodemographic characteristics
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Table 2 shows the adjusted relative risks of post-concussion symptoms at 7 and 90 days post-injury. We found no difference between the two groups regarding our primary outcome, the risk of having three symptoms or more on the Rivermead Post-concussion questionnaire at 90 days (RR: 0.8 [95% CI 0.62–1.08]). There also was no difference regarding the risk of having a total score of 21 points or more at 7 (RR: 1.1 [95% CI 0.76–1.45]) and 90 days post-injury (RR: 0.5 [95% CI 0.29–1.00]).

Table 2 Impact of injury mechanism (sport vs non-sport) on post-concussion symptoms at 7 days and 90 days post-mild TBI
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Fig. 1
figure 1

Flow chart

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At 7 days, patients from the sports-related mild TBI group were at higher risk of experiencing poor concentration (RR: 1.3 [95% CI 1.05–1.54]), but at 90 days this difference can no longer be observed. At 90 days post-injury, those patients were at lower risk of fatigue (RR: 0.7 [95% CI 0.51–0.98]) and dizziness (RR: 0.6 [95% CI 0.35–0.99]).

The impact of the mechanism of injury (sport versus non-sport) on patients’ normal daily activities is shown in Table 3. Patients in the sports-related mild TBI group were at higher risk of non-return to their normal daily activities due to post-concussion symptoms at 7 days post-injury (RR: 1.1 [95% CI 1.01–1.22]) and more specifically, to their sports activities (RR: 2.2 [95% CI 1.69–2.94]). However, this was no longer observed 90 days post-injury.

Table 3 Impact of injury mechanism (sport vs non-sport) on patient’s normal activities at 7 days and 90 days post-injury
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Discussion

Interpretation of findings

This study provides new knowledge regarding the evolution of post-concussion symptoms and illustrates potential differences between sports-related mild TBI and other mechanisms of injury. Indeed, returning to their normal daily activities, especially sports, seems to be more difficult at 7 days for patients who sustained a sports-related mild TBI. However, this is no longer observed 90 days post-injury. Most importantly, patients who sustained a sports-related mild TBI appear to be at lower risk of experiencing symptoms such as fatigue and dizziness at 90 days post-injury. Patients from that group also seem to experience fewer symptoms at 90 days post-injury, although this difference was not statistically significant.

Comparison to previous studies

Our results concur with those of two other studies. Indeed, Sieger et al. found high school athletes aged 13–21 years who suffered sports-related mild TBI (football and soccer) recovered more quickly than others who were involved in a motor vehicle collision [19]. A recent study carried out by Beauchamp et al. among children aged 6–18 years also highlighted that those who sustained sports or recreational-related concussions had a better quality of life and were less likely to experience persistent post-concussion symptoms and cognitive impairment. [11] Both studies suggest that these differences could be explained by particular biomechanical characteristics (velocity of impact, distribution of the forces, location and speed) which potentially differ between motor vehicle collision, bicycle accidents or falls and sports injury. As recently shown, brain tissue stresses and strains are related to the impact force of the injury [31]. Thus, some studies suggest that the amount of pathological brain damage influences the neurological dysfunction severity, which could be reflected by the intensity and duration of post-concussion symptoms [32].

However, the literature is inconsistent regarding the impact of mechanism of injury on patient recovery. In fact, a retrospective study by Tator et al. suggests that the mechanism of injury did not predict the number of symptoms and the recovery time [18]. This study included patients who were referred to one neurosurgeon with a specific interest in post-concussion symptoms. Even if the referral criteria are unknown, these patients were most likely suffering from more complicated and persistent post-concussion symptoms, thus affecting the generalizability of the study.

Strengths and limitations

Our study has limitations. First, the exposure factor (mechanism of injury) could not be controlled. Therefore, this kind of research question cannot be answered with a prior randomization, thus forcing the use of a prospective observational study design. This may explain why the sample size of the sports-related mild TBI cohort were just under a third of the non-sports-related mild TBI cohort. In the literature, more than half of the mild TBI are usually due to sports injury [4]. This discrepancy may be caused by the fact that our cohort includes older patients. In addition, sports-related mild TBI patients may be more likely to be managed by sports team physiotherapists or doctors instead of going to the ED. Furthermore, groups differed significantly in some of their initial characteristics, especially age, which had a non-linear relation with our main study outcome. The groups were also very different for prescribed medications which suggests a difference in baseline health. However, statistical adjustments were performed for all potentially confounding factors. Data regarding pre-mild TBI level of physical activity and the recovery process was not available. Nonetheless, we can probably infer patients that sustained sports-related mild TBI were more active. This lack of information limits our capacity to interpret the differences observed. Lastly, since 3 months is often the minimal duration time to considerer a symptom as persistent [33], it would have been interesting to extend the follow-up duration to have a more long-term vision of the patients’ clinical course and thus, see if differences in the recovery of both groups remained or even increased.

However, our study had several strengths such as a very large sample of non-hospitalized mild TBI patients. All data were collected on a prospective basis through phone interviews conducted by experienced research assistants, which brought better internal validity to the study than self-administered questionnaires. The multicenter nature of our study and the fact that patients from different levels of trauma centers across Canada ensured that our participants are representative of mild TBI patients seen in the ED.

Clinical implications

Recent studies suggest that early controlled sub-symptom threshold aerobic exercise might be more beneficial than rest in mild TBI recovery [10, 34,35,36,37,38,39]. Physically active individuals could somehow be protected from a poor outcome and recover faster as they are probably more inclined to progressively return to physical activities during their rehabilitation. Their medical follow-up may be more comprehensive and they might also enjoy a better state of physical and mental health [40]. Therefore, being physically active during rehabilitation, coupled with a more structured follow-up may prevent, or at least lessen the post-concussion symptoms. Of course, further research is needed to support this, and to further improve treatment recommendations for mild TBI management.

Research implications

Since information regarding the patients’ rehabilitation process have not been collected, more research is needed to better understand the underlying causes of the differences observed to improve post-ED mild TBI patient management.

Conclusion

This study identified potential differences in the clinical course of mild TBI patients depending on the mechanism of injury. Indeed, patients who sustained sports-related injury seemed to experience less fatigue and dizziness 90 days post-injury. These differences should be considered when planning post-ED care, as clinicians should be mindful that non-sports-related mild TBI patients may experience more post-concussion symptoms and that the level of physical activity may influence the patient’s rehabilitation.