Multiple review articles involving sports-related concussion call for more research regarding sex and its role in the recovery from concussion.
4,5,11-13 The current study seems to be the first to suggest a statistically significant difference in length of recovery between male and female athletes in middle school and high school with first-time, sports-related concussions.
A preponderance of current literature states that 80% to 90% of sports-related concussion symptoms resolve in 7 to 10 days.
5-10 However, many of these studies involved male collegiate or professional football players. A 2014 study looking at patients with an average age of 14.3 years showed concussion symptoms to last a median of 13 days.
14 However, this study did not evaluate data by sex, and its sample was 57.4% male. Kadyan et al
15 found no differences between sexes in duration or frequency of symptoms; however, their population differed, consisting of patients with traumatic brain injury in an acute rehabilitation setting with a mean age of 35 years, whereas the present study involved patients aged 11 to 18 years. In a retrospective medical record review, Cantu et al
16 found no differences in recovery from concussion between sexes. The average age of the participants in that study was approximately 19 years. The current study's findings that male and female athletes reported symptoms for a median of 11 and 28 days, respectively, are in agreement with the most recent consensus statement from the 5th International Conference on Concussion in Sport: “[T]he large majority of injured athletes recover,
from a clinical perspective, within the first month of injury
.”
6
In another retrospective medical record review, Kostyun and Hafeez
17 showed that adolescent female athletes had a longer recovery course than adolescent male athletes (75.6 [73.0] and 49.7 [62.0] days, respectively [
P=.002]) and required more interventions after concussion. The only major difference between their study and the current study was that we focused on first-time concussion, whereas Kostyun and Hafeez
17 included athletes with a history of multiple concussions. Also, we looked at medians instead of means because of the skewing effect of outliers. These differences could explain the longer recovery reported in their sample compared with ours.
To our knowledge, no definitive research has provided an explanation for sex differences in concussion recovery. We think that these differences are complex and multifactorial, including biomechanical and biological differences between the sexes.
11,18-20 Biomechanically, females may be at higher risk for concussions because their necks are smaller and do not absorb shock as well as the necks of males. One study of collegiate soccer players found that females had 26% less total mass in their head and neck, and displayed significantly greater head-neck segment peak angular acceleration and displacement.
18 Biologically, it has also been suggested that females have a greater basal rate of glucose metabolism.
19 Broshek et al
20 suggested that as a result of increased demands for glucose after a concussion, female athletes might exhibit prolonged impairments compared with male athletes because females have a greater basal rate of glucose metabolism.
The prevalence of other medical conditions, such as migraines and mood disorders, in men and women may also potentially explain differences in concussion recovery.
21-23 Migraine is more than twice as common in females than in males, and females experience more frequent, longer-lasting, and more painful attacks.
21 In addition, history of migraine has been associated with prolonged concussion recovery.
6,22 Our research showed a statistically significant difference in preinjury history of migraine/frequent headaches in females compared with males. However, we found no statistically significant difference between females with a history vs those without a history of migraines/frequent headaches in median time being symptomatic after concussion (26 days vs 28 days, respectively;
P=.806). The lack of a significant difference may have been because physicians adjust their management of concussion based on an athlete's medical history.
After puberty, females experience major depression at roughly twice the rate of males.
23 The lifetime prevalence of generalized anxiety disorder is also higher in females than in males (6.6% vs 3.6%, respectively),
24 and females may have greater anxiety sensitivity than males.
25 A recent consensus statement
6 indicates that such psychological factors may increase concussion symptom recovery and contribute to risk of persistent symptoms of concussion.
Mental stress could certainly play a role in concussion recovery, and adolescent girls may have higher levels of stress than boys.
28,29 The effects of stress include headache, nausea, fatigue, anxiety, irritability, difficulty sleeping, and difficulty concentrating. These effects are also concussion symptoms and thus could potentially account for a longer recovery in females with concussion.
Children, adolescents, and young adults with a history of headache disorder or mental health problems seem to be at greater risk of having concussion symptoms for more than 1 month.
6 We theorize that it is a possibility that some first-time concussions in adolescent athletes with persistent symptoms are due to preexisting medical conditions or psychosocial complications, regardless of sex. In other words, it is possible that the concussion has resolved and the “persistent concussion symptoms” could possibly be better attributed to another medical condition or psychosocial dysfunction. The most recent consensus statement
6 on concussion in sport goes on to state that, “‘Persistent symptoms’ does not reflect a single pathophysiological entity, but describes a constellation of non-specific posttraumatic symptoms that may be linked to coexisting and/or confounding factors, which do not necessarily reflect ongoing physiological injury to the brain.” Considering medical history is often dependent on the patient self-reporting, it is certainly possible that the current study contained an incomplete dataset with respect to preinjury diagnoses. Psychosocial problems can also be ambiguous and difficult for physicians to assess if not conveyed by patients.
When matched for sex, the current study found no statistically significant difference in length of recovery when comparing sports. The incidence was highest in football players for males and soccer players for females, consistent with preexisting data.
1,2
Little concussion research has been performed in children younger than 13 years.
6 We found no significant difference in length of recovery between middle school athletes (aged 11-13 years) and high school athletes (aged 14-18 years). Interestingly, although not statistically significant, we found the middle school athletes recovered more quickly than the high school athletes. Lee et al
30 found no statistically significant difference in symptom presence after a sports-related concussion when comparing 92 high school athletes with 92 collegiate athletes matched for sex and number of previous concussions. Conversely, a study by Zuckerman et al
31 showed that adolescents aged 13 to 16 years took longer to return to their neurocognitive and symptom baselines than adults aged 18 to 22 years.
31 The findings of Cantu et al
16 suggest that participants aged 18 years or older are more likely to report symptoms that last longer than 90 days than participants younger than 18 years.
16 The most recent consensus statement recognizes that pediatric populations in general take more time to recover from a concussion than adults, and they recommend that the diagnosis of “concussion with persistent symptoms” not be used in children until symptoms have been present for longer than 4 weeks.
6 Further research needs to be done when it comes to concussion recovery and age, considering the present conflicting data and lack of data on persons younger than 13 years.