Abstract
Context
Concussions incurred during high school athletics are a significant health concern, and studies examining concussions with a symptom resolution time (SRT) of 15 to 28 days have been limited.
Objective
To compare concussions that had an SRT of 15 to 28 days with concussions that had an SRT of greater than 28 days among US high school athletes.
Design
Descriptive epidemiology study.
Setting
Secondary school athletic training clinics.
Patients or Other Participants
Secondary school athletes.
Main Outcome Measure(s)
Concussion frequency, symptom number, and symptom prevalence.
Results
Among all 917 reported concussions (of which 50.8% had missing SRT), 88 had an SRT recorded as 15 to 28 days, and 29 had an SRT recorded as greater than 28 days. Greater frequencies of concussions with an SRT of 15 days or more were reported in boys’ sports (n = 78) than girls’ sports (n = 39). Boys’ football (51.7%) and girls’ basketball (11.5%) accounted for the largest proportions of all reported concussions with an SRT of 15 to 28 days; boys’ football (58.6%) accounted for the greatest proportion of concussions reported with an SRT greater than 28 days. The average number of symptoms was 6.3 ± 3.4 for concussions with an SRT of 15 to 28 days and 7.2 ± 3.8 for those with an SRT greater than 28 days. The most frequently reported symptoms in concussions with both SRT of 15 to 28 days and greater than 28 days were headache, dizziness, sensitivity to light, and difficulty concentrating. The prevalence of irritability was higher in concussions with an SRT of 15 to 28 days as compared with concussions with an SRT greater than 28 days (26.1% versus 13.8%); visual problems (48.3% versus 35.2%) and hyperexcitability (24.1% versus 15.9%) were more prevalent in concussions with an SRT greater than 28 days, although differences were not statistically significant.
Conclusions
Symptom prevalence and total count were comparable between concussions with an SRT of 15 to 28 days and those with an SRT of greater than 28 days with no statistically significant difference, suggesting that symptom burdens within these groups are more similar than they are different.
Keywords: pediatric, adolescent, head injuries, youth sports, mild traumatic brain injury
Key Points
Concussions with a symptom resolution time of 15 to 28 days and those with a symptom resolution time of greater than 28 days did not exhibit a statistically significant difference in the number of symptoms or in symptom presentation.
The distribution of concussions with a symptom resolution time of 15 to 28 days and those with a symptom resolution time of greater than 28 days was similar by event type, gender, mechanism, and injury history.
Concussions are an important health concern in the pediatric population. Sport-related concussions (SRCs) are a subset of traumatic brain injury and result from direct trauma or indirect trauma resulting in a secondary force transmitted to the head.1 These injuries elicit impairment of neurological functioning and various symptoms, with or without loss of consciousness.1,2 The highest rate of concussions among pediatric patients is observed among those aged 15 to 19, and approximately 15.1% (2.5 million) of high school students experience a concussion secondary to a sport or physical activity.3,4
According to the American Association of Pediatrics, symptoms associated with SRCs can be classified into 5 categories: somatic, vestibular and/or oculomotor, cognitive, emotional, and sleep.2 Common symptoms endorsed include headache, dizziness, difficulty concentrating, and irritability.2,5 Prior authors have observed notable concurrent symptom presentations, such as light and noise sensitivity, and researchers have also suggested that the environment in which the evaluation of SRC occurs may also influence symptom endorsement.6 Additionally, higher symptom burden and specific symptoms such as retrograde amnesia, difficulty concentrating, and visual disturbance have been associated with a prolonged recovery.7,8
Research has shown that symptom resolution for most patients with a concussion occurs within 7 to 10 days, with a mean symptom duration of 6.43 days for high school athletes.9,10 These data also show that between 18.3% and 24.8% of pediatric patients reported symptoms after 1 month of onset.9 Postconcussive syndrome (PCS) occurs when concussion symptoms persist for a prolonged period of time, typically greater than 28 days, but the minimum symptom duration that defines PCS has varied in prior studies from 28 days to 3 months.8,11–13 In a survey of 597 physicians, the duration of PCS was defined variably from less than 10 days to less than 3 months, with the majority defining it as greater than 1 month.14 Notably, the mean number of symptoms averages 6.7 in PCS; this is higher than that in concussions overall, which average 4.7 to 5.6 symptoms in high school athletes.5,8,15
The consequence of largely defining PCS as a symptom resolution time (SRT) of greater than 28 days is that concussions with an SRT of 15 to 28 days have been underexplored. Notably, there is a paucity of studies exploring the symptomatology of concussions with an SRT of 15 to 28 days in adolescents. This is of interest, because about 37% of high school players continue to experience symptoms past the acute period of 7 to 14 days, with about 23% having an SRT of 15 to 28 days and about 14% having an SRT greater than 28 days.6,16 Because treatment for PCS can be multipronged, including medications, neuropsychiatric evaluation, cognitive therapy, vestibular therapy, activity modifications, and academic accommodations, understanding the symptoms of adolescents with an SRT of 15 to 28 days may lead to more comprehensive care for this population.9 We sought to better characterize the epidemiology, symptom prevalence, and duration of concussions with an SRT of 15 to 28 days and those with an SRT greater than 28 days in high school athletes to help guide both evaluation and treatment.
Methods
Study Data
In this retrospective study, we analyzed data reported to the National Athletic Treatment, Injury and Outcomes Network Surveillance Program (NATION-SP) between 2014–2015 and 2018–2019. The NATION-SP (managed by the Datalys Center for Sports Injury Research and Prevention, Inc) captures sport-related time-loss and non–time-loss injuries sustained by high school student-athletes for 27 different high school sports. The methods of the NATION-SP have been reviewed and approved by the Western Institutional Review Board (Puyallup, WA) and have been previously described in detail; they are outlined below.17 Briefly, athletic trainers (ATs) at participating high schools responsible for practice and game coverage reported exposure and injury data using their respective electronic medical record systems across the academic year. A reportable health event (including SRCs retained in the present study) was defined within the NATION-SP as (1) having resulted from participation in a high school–sanctioned practice or competition and (2) having needed medical attention by an AT or other medical professional (ie, physician) regardless of time loss. Injuries that resulted from activities outside of practices and competitions were excluded from this analysis. Participating ATs were not provided specific criteria for reporting concussions, though concussion consensus statements1,18,19 were available to all sports medicine staff during the entirety of the study. Symptom presentations were captured as dichotomous variables and at a single time point within NATION-SP. Symptom resolution time was defined as the number of days from the injury date to the point of complete resolution of all symptoms and was characterized as an ordinal variable within the surveillance system.
Statistical Analysis
Sport-related concussions reported to NATION-SP during 2014–2015 to 2018–2019 were retained in this analysis. Data were first analyzed to describe the distribution of reported SRCs across sports (overall and then stratified by SRT [15 to 28 days and greater than 28 days]) using frequencies (and percentages). We then examined the distribution of SRCs (stratified by SRT) by event type (practice versus competition); injury mechanism (player contact versus other contact); and injury history (new versus recurrent). Symptom prevalence by SRT group was described using frequencies (percentages). Differential distributions of SRC SRTs between explanatory variables and differential symptom prevalence between SRT groups of interest were examined using Pearson χ2 tests (or Fisher exact tests when needed). Finally, summary statistics (mean ± SD and median with interquartile ranges) were used to describe the total number of symptoms reported by SRT groups. Wilcoxon rank sum tests were used to examine group differences (between SRT groups) in the total number of symptoms reported. As approximately 50% of reported SRCs were missing an SRT, sensitivity analyses were performed to examine potential differences across gender, event type, injury mechanism, and injury history between SRC records with and those without an SRT (Table 1). Statistical significance was evaluated at the .05 level, and all analyses were conducted using SAS 9.4 (SAS Institute).
Table 1.
Distribution of Sample Characteristics by Sport-Related Concussion Records With and Without Symptom Resolution Time (SRT) Among High School Athletes During the 2014–2015 to 2018–2019 Academic Yearsa
| Characteristic | Overall (N = 917) | Missing SRT (N = 466) | Not Missing SRT (N = 451) | P Valueb |
|---|---|---|---|---|
| Gender, No. (%) | .50 | |||
| Male | 641 (69.90) | 311 (68.96) | 330 (70.82) | |
| Female | 272 (29.66) | 139 (30.82) | 133 (28.54) | |
| Missing | 4 (0.44) | 1 (0.22) | 3 (0.64) | |
| Event type, No. (%) | .01 | |||
| Competition (game) | 574 (62.60) | 310 (66.52) | 264 (58.54) | |
| Scheduled team practice (varsity) | 343 (37.40) | 156 (33.48) | 187 (41.46) | |
| Injury mechanism, No. (%) | .60 | |||
| Player contact | 553 (60.31) | 273 (58.58) | 280 (62.08) | |
| Other contact | 313 (34.13) | 166 (35.62) | 147 (32.59) | |
| Other/unknown | 51 (5.56) | 27 (5.79) | 24 (5.32) | |
| Injury history, No. (%) | .80 | |||
| New | 833 (90.84) | 413 (91.57) | 420 (90.13) | |
| Recurrent | 78 (8.51) | 35 (7.76) | 43 (9.23) | |
| Missing | 6 (0.65) | 3 (0.67) | 3 (0.64) |
Denotes symptom prevalence among all reported concussions with and without resolution time data.
Pearson χ2 test; Fisher exact test.
RESULTS
SRC Frequencies by Sport
Overall, 917 SRCs were reported during the 2014–2015 to 2018–2019 academic years (50.8% had missing SRT). Among all SRCs, 477 (52.0%) were reported in boys’ football, 76 (8.3%) in girls’ basketball, 60 (6.54%) in girls’ soccer, 55 (6.00%) in girls’ lacrosse, and 49 (5.33%) in girls’ volleyball. Among all SRCs, 49.2% were reported with an SRT (n = 451; Table 1). A majority of SRCs were reported in competitions (n = 574, 62.6%), were attributed to player contact (n = 553, 60.3%), and were new injuries (n = 833, 90.8%).
In 88 (9.6%) of all reported SRCs, symptoms resolved within 15 to 28 days. In 29 (3.2%) of all reported SRCs, symptoms resolved in 28 days or longer. Sport-related concussions with an SRT of 15 to 28 days and those with an SRT of greater than 28 days were most commonly reported in boys’ football (SRT 15–28 days = 51.7%, SRT > 28 days = 58.6%), followed by girls’ basketball (SRT 15–28 days = 11.3%, SRT > 28 days = 0%) and girls’ soccer (SRT 15–28 days = 6.9%, SRT > 28 days = 10.3%). We observed no differences in the distribution of 15- to 28-day SRCs or >28-day SRCs by boys’ and girls’ sports.
Distribution of SRCs by SRT, Event Type, Gender, Mechanism, and Injury History
Sport-related concussions with an SRT of 15 to 28 days as well as those greater than 28 days were comparably distributed by gender among both practice- and competition-related SRCs (Table 2). Similar results were seen by injury mechanism as well as by injury history. In both practices and competitions, 15- to 28-day SRCs as well as greater than 28-day SRCs were more prevalently attributed to player contact mechanisms and reported as new injuries. A lower proportion of practice-related SRCs were reported with SRTs as compared with competition-related SRCs (Table 1).
Table 2.
Distribution of Concussions by Symptom Resolution Time Across Gender, Mechanism, and Injury History in High School Athletes, 2014–2015 to 2018–2019a
| Gender |
Injury Mechanism |
Injury History |
||||
|---|---|---|---|---|---|---|
| Male | Female | Player Contact | Other Contact | New | Recurrent | |
| Practice, No. (%) (n = 55)b | ||||||
| 15–28 d | 25 (65.79) | 13 (34.21) | 24 (63.16) | 12 (31.58) | 37 (97.37) | 1 (2.63) |
| >28 d | 12 (70.59) | 5 (29.41) | 11 (64.71) | 6 (35.29) | 16 (94.12) | 1 (6.88) |
| Competition, No. (%) (n = 62)c | ||||||
| 15–28 d | 32 (64.00) | 18 (36.00) | 29 (65.91) | 15 (34.09) | 47 (94.00) | 3 (6.00) |
| >28 d | 9 (75.00) | 3 (25.00) | 7 (58.33) | 4 (33.33) | 12 (100.00) | 0 (0.00) |
Concussions included had a symptom resolution time of 15–28 days or greater than 28 days.
Represents covariate distributions based on all concussions reported with a particular resolution time (15–28 days or >28 days) in practices.
Represents covariate distributions based on all concussions reported with a particular resolution time (15–28 days or >28 days) in competitions.
Symptom Prevalence
Among SRCs with an SRT of 15 to 28 days and those with an SRT of greater than 28 days, the most prevalently reported symptoms were headache (SRT 15–28 days = 92.1%, SRT > 28 days = 96.6%) and dizziness (SRT 15–28 days = 72.7%, SRT > 28 days = 82.8%). A larger proportion of athletes with an SRT of 15 to 28 days than with an SRT greater than 28 days exhibited irritability (26.1% versus 13.8%), whereas greater proportions of players with an SRT of greater than 28 days than with an SRT of 15 to 28 days exhibited retrograde amnesia (13.8% versus 5.7%), hyperexcitability (24.1% versus 15.9%), and tinnitus (20.7% versus 11.4%; Table 3). Differential symptom prevalence across SRT groups was not statistically significant. Among SRCs with SRTs of 15 to 28 days, the average number of symptoms reported was 6.3 ± 3.4, and among SRCs with SRTs of greater than 28 days, the average number of symptoms reported was 7.2 ± 3.8; we observed no statistically significant differences among the average number of symptoms endorsed.
Table 3.
Distribution of Concussion Symptoms by Symptom Resolution Time in High School Athletes, 2014–2015 to 2018–2019
| Symptoms | Symptom Prevalence, No. (%)a |
P Value | |
|---|---|---|---|
| 15–28 d (n = 88) | >28 d (n = 29) | ||
| Posttraumatic amnesia | 3 (3.00) | 4 (13.79) | .06 |
| Retrograde amnesia | 5 (5.68) | 4 (13.79) | .22 |
| Difficulty concentrating | 52 (59.09) | 19 (65.52) | .49 |
| Disorientation | 22 (25.00) | 8 (27.59) | .74 |
| Dizziness | 64 (72.73) | 24 (82.76) | .39 |
| Headache | 81 (92.05) | 28 (96.55) | .57 |
| Hyperexcitability | 14 (15.91) | 7 (24.14) | .41 |
| Irritability | 23 (26.14) | 4 (13.79) | .29 |
| Loss of consciousness | 4 (4.55) | 1 (3.45) | 1.00 |
| Nausea | 34 (38.64) | 10 (34.48) | .75 |
| Tinnitus | 10 (11.36) | 6 (20.69) | .22 |
| Balance problems | 41 (46.59) | 15 (51.72) | .98 |
| Visual problems | 31 (35.23) | 14 (48.28) | .13 |
| Sensitivity to light | 56 (63.64) | 21 (72.41) | .61 |
| Sensitivity to noise | 43 (48.86) | 15 (51.72) | .67 |
| Insomnia | 13 (14.77) | 6 (20.69) | .41 |
| Drowsiness | 40 (45.45) | 15 (51.72) | .75 |
| No. of symptoms | |||
| Mean ± SD | 6.3 ± 3.4 | 7.2 ± 3.8 | |
| Median (interquartile range) | 6.00 (6.00) | 6.00 (5.5) | .33 |
Denotes symptom prevalence among all reported concussions with a particular resolution time (15–28 days or >28 days).
DISCUSSION
We sought to compare concussions with an SRT of 15 to 28 days and concussions with an SRT of greater than 28 days across injury characteristics and resulting concussion symptoms. There were several epidemiological parallels between these 2 groups, and overall, individual symptom prevalence and total count were comparable between SRT groups. However, there were also unique and potentially clinically significant symptom features that may be used to guide the evaluation and management of concussions in high school sports.
The distributions of concussions by injury mechanism, injury history, and event type were similar among concussions with an SRT of 15 to 28 days and those with an SRT greater than 28 days. Additionally, we found a high prevalence of SRCs attributable to player contact (versus other contact), which has been found previously.16,20 Symptom resolution times of 15 to 28 days as well as those of greater than 28 days were most commonly reported in boys’ football, girls’ basketball, girls’ soccer, and girls’ volleyball. We also observed a higher prevalence of SRCs with an SRT of greater than 15 days among male athletes than female athletes, which may be due to the large proportion of SRCs incurred by male football players. In our dataset, 51.7% of reported SRCs with an SRT of 15 to 28 days and 58.6% of reported SRCs with an SRT greater than 28 days were attributable to football. Based on surveillance data captured during 2011–2012 to 2013–2014, Kerr et al reported that 45% of PCS concussions were attributed to football athletes. Although our findings are largely in alignment, we note that a higher proportion of SRCs with an SRT of greater than 28 days was attributed to boys’ football in the present study.8 However, our sample size was too small to evaluate distributions of SRCs in gender-comparable sports, and the association of gender with PCS has been mixed in the literature.8,11,12
We found the mean number of symptoms in concussions with an SRT of 15 to 28 days and those with an SRT greater than 28 days to be comparable to each other in our study and also higher than the average noted previously in the literature for concussions overall.8,15 This may suggest that concussion symptoms with an SRT of 15 to 28 days are more similar to PCS symptoms with an SRT greater than 28 days. Other researchers have found a greater number of mean symptoms in PCS compared with all concussions, and greater symptom burden has been associated with prolonged recovery and PCS.2,7,8,13,21
Additionally, the prevalences of the most common symptoms, including headache, dizziness, and difficulty concentrating, were comparable in concussions with an SRT of 15 to 28 days and those with an SRT greater than 28 days in our study, further suggesting parallels between concussions with these recovery periods. Although these are also among the more commonly reported symptoms in concussions among high school athletes, symptoms of sensitivity to light, sensitivity to noise, and drowsiness were reported with greater prevalence in concussions with an SRT of 15 to 28 days in our study than were reported in several studies for concussions overall.6,15,16 Furthermore, difficulty concentrating and sensitivity to noise are among factors previously associated with PCS.8 Although concussions with an SRT greater than 28 days exhibited greater prevalence of retrograde amnesia (13.8% versus 5.7%), hyperexcitability (24.1% versus 15.9%), and tinnitus (20.7% versus 11.4%) compared with concussions with an SRT of 15 to 28 days, these differences were not statistically significant. Additionally, there was no statistical difference in the average number of symptoms between concussions with an SRT of 15 to 28 days and those with an SRT greater than 28 days, suggesting that symptom burdens within these groups are more similar than they are different.
Both the number and types of symptoms experienced by high school athletes with concussions with an SRT of 15 to 28 days may be clinically significant. One impact of concussions on adolescents is a temporary worsening of other underlying medical conditions, such as migraines, attention-deficit/hyperactivity disorder, learning disorders, and depression, but it is important to realize that these conditions can also mimic concussion symptoms.2 Additionally, it is possible that attention-deficit/hyperactivity disorder, mood disorders, migraines, and learning disabilities increase risk for prolonged symptom resolution, although the literature is inconclusive.7,11,22 Moreover, medical treatment for PCS can be multidisciplinary and may involve a primary health care team, cognitive therapists, sleep hygiene, and activity modifications.9,21 Considering a more robust approach for adolescent patients with an SRT of 15 to 28 days may help them manage their symptoms better and possibly facilitate recovery.
Cognitive symptoms can both develop after the initial presentation of concussion and affect the majority (44%–56.8%) of pediatric patients 7 days after presentation.23 Our study showed that difficulty concentrating, retrograde amnesia, and disorientation occurred comparably in concussions with an SRT 15 to 28 days and an SRT greater than 28 days in high school athletes. Although we could not evaluate the duration of each specific symptom, it remains important to understand that these symptoms may be present well beyond the initial event so that adolescents can receive appropriate academic and emotional support.
Several researchers have found that concussions can affect academic performance.24–26 For example, high school athletes with concussions had greater difficulty with math than college students with concussions.25 Additionally, a younger age was correlated with a shorter time period of academic engagement before concussion symptoms returned or worsened.25 High school athletes were also more likely to have a lower grade point average and suffer from self-reported cognitive impairment than students without a concussion.24 Notably, Purcell et al found that a greater symptom burden, including difficulty concentrating, which was prevalent among both SRT groups in the present study, is associated with challenges returning to school.26 Other symptoms reported in our study, such as drowsiness and nausea, may further complicate return-to-learn time, even in SRCs with an SRT of 15 to 28 days. Consequently, it is recommended that adolescents return to school before play with academic accommodations to avoid cognitive stress and triggers that exacerbate symptoms.2,9,21,27 They may also benefit from involvement with a concussion management team that includes the family and medical and academic members to facilitate scholastic accommodations.28
Additionally, we found that hyperexcitability, irritability, and insomnia were among the symptoms reported in high school athletes with concussions both with an SRT of 15 to 28 days and greater than 28 days. These can be elements of both routine adolescent behavior and an underlying SRC. Although ATs were involved in assessing athletes in our dataset, the potential for concussions to go undiagnosed exists in practice and competitive settings without ATs or other health professionals. Furthermore, adolescents may believe that their concussion symptoms are not severe enough to report or may avoid reporting concussions for fear of letting down coaches and teammates.29 Consequently, if athletic adolescents present with behavioral and academic changes from their baseline, it is important to consider an undiagnosed concussion, particularly when affective changes may be misattributed to typical teenage behavior.
Our study showed no statistically significant difference in symptom burden between concussions with an SRT of 15 to 28 days and those with an SRT greater 28 days. Although PCS has previously been defined as an SRT greater than 28 days, redefining the time frame of PCS to concussions with an SRT of 15 days or greater may be warranted to address the clinically significant symptoms that high school athletes with SRTs of 15 to 28 days continue to experience. Alternatively, concussions with an SRT of 15 to 28 days can receive their own designation, such as “persistent concussion.” More research exploring the impact of SRCs with SRTs greater than 14 days’ duration could benefit the pediatric population. Determinants of precise SRT time frames, as well as the academic and emotional implications of various SRT periods, are potential areas for further exploration.
There are several limitations to our study. Although the NATION-SP offers insight into athletic injuries incurred across numerous states, it fails to represent all sports or every state, which restricts external validity and application to other play settings, such as recreational leagues. Additionally, participation varies year to year, which may affect the stability of our estimates. High school athletes may also coparticipate in recreation or travel leagues in the same or a different sport and may experience more injury-risk exposures compared with high school athletes who exclusively play high school sports. Although the database is based on clinical documentation from ATs, recording of symptoms that are not easily observed or measured, such as self-reported headaches, may be subject to response bias during examinations. Similarly, initial concussion symptoms are captured at only a single point during the acute-subacute period, which may inherently result in missed symptoms at diagnosis and may not capture symptom-specific resolution times.30 The proportion of reported SRCs with missing SRTs presents another limitation of our study, and this may be related to data collection procedures in injury surveillance. That said, contextual characteristics (eg, event type) between SRC records with and without SRTs were observed. Furthermore, some of our findings may be attributable to the significant proportion of concussions incurred by male football players, which was 52.0% of concussions overall, 51.7% of concussions with an SRT of 15 to 28 days, and 58.6% of concussions with an SRT greater than 28 days. Future researchers could broaden analytical samples as possible, evaluate concussions with various SRTs, and track the onset and resolution of each symptom longitudinally until all symptoms resolve.
CONCLUSIONS
High school athletes continue to be at risk for concussions. Concussions with an SRT of 15 to 28 days and an SRT greater than 28 days demonstrate parallel symptom profiles with few differences between them in regard to symptom prevalence or average number of symptoms. Concussions with an SRT of 15 to 28 days can present with a clinically significant symptom burden that can inform management by a student’s athletic coach, academic teacher, and health care team. High school athletes would benefit from future studies evaluating the impact of concussions with an SRT greater than 14 days.
ACKNOWLEDGMENTS
This study would not have been possible without the assistance of the many high school ATs who participated in the program. The NATA is a founder and continuing sponsor of the NATION-SP. The content of this report is solely our responsibility and does not necessarily reflect the views of the funding organization.
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