Although sex-based differences regarding the incidence of traumatic brain injury (TBI) have been well documented, there is a dearth of literature examining sex and gender effects on TBI-related outcomes and related gender-specific issues. Of note, much of the existing literature discusses gender and sex interchangeably. The National Institutes of Health (NIH) defines sex as “biological differences between females and males, including chromosomes, sex organs, and endogenous hormonal profiles,” whereas gender is defined as “socially constructed and enacted roles and behaviors which occur in a historical and cultural context and vary across societies and over time.” Perhaps the complex interplay between sex and gender can help explain some of the inconsistencies found in sex and gender-based TBI research. There is a need for future studies specifically examining sex and gender differences in TBI to help elucidate the full extent of their effects.
Epidemiology
The international incidence of TBI is reported to be 349 per 100,0000 person-years. When analyzed by sex, the annual incidence of TBI among females is 195 per 100,000 compared with 388 per 100,000 for males. In the United States, rates of TBI-related emergency department visits by sex in 2010 showed an average of 800 per 100,000 visits for males versus 633.7 per 100,000 for females. When examining the rates of TBI-related deaths, men had over twice the rate of deaths compared with women between the years of 2001 and 2010. Additionally, men had nearly double the rate of TBI-related hospitalizations compared with women between 2001 and 2010, suggesting men may be at higher risk of suffering a more severe brain injury.
The relative risk of sustaining a TBI is near equal for males and females below the age of 2 and over the age of 65. , The largest discrepancy is found between the ages of 10 and 14, with males having the highest risk for TBI. ,
Outcomes
Studies on gender-related outcomes after TBI have explored the effects of hormonal influences, including the potential neuroprotective effects of the steroid sex hormones estrogen and progesterone. Animal studies have shown neuroprotective effects of both, but attempts to replicate these findings in clinical studies have yielded conflicting results. A shorter duration of amenorrhea after TBI has been found to be associated with improved outcomes, with subjects experiencing a longer durations of amenorrhea found to have worse global outcome ratings when controlling for severity of injury. , These findings could be attributed to protective effects of female sex hormones. , However, other studies have shown evidence of higher mortality and worse functional outcomes in women after moderate to severe TBI. , Additional research has shown peri- and postmenopausal women as having reduced mortality and fewer complications after moderate to severe TBI, whereas premenopausal women exhibit similar mortality rates as men. , More research is needed to further explore the effects of sex hormones in relation to TBI outcomes.
Sports-related concussion
Gender differences have also been reported regarding sports-related concussion incidence, clinical presentation, and recovery. Data indicate an overall higher incidence of concussion among women compared with that of men in sports played with the same rules. Although controversial, some studies suggest the increased incidence of sports-related concussion in females is related to reporter bias, because males were found to have less intent to report future concussions than their female counterparts. , This may be because of differences in gender norms as opposed to biologically determined sex, because female athletes with greater conformity to the norms of risk-taking behavior were more likely to return to play while symptomatic, and intent to report future concussions was greater among athletes who conformed less to traditional masculine gender norms of self-reliance and winning.
One proposed explanation for the increased incidence relates to the biomechanical differences between men and women, specifically head-to-neck ratio, neck strength, and dynamic stability. Weaker neck strength was found to correlate with athletes who had sustained a concussion.
In terms of outcome and recovery, females appear to take longer to recover than their male counterparts and experience more severe and longer lasting neuropsychological deficits relative to baseline than do males.
Intimate partner violence
Whereas consequences of mild TBIs (mTBI)—in particular sports-related mTBIs—have gained increased international attention, TBI related to intimate partner violence (IPV) has garnered relatively little recognition in comparison. The paucity of research on IPV-related TBI is confounded by hesitancy of victims to disclose abuse or seek medical treatment and the lack of uniform screening guidelines. IPV is highly gendered and is a common cause of TBI because head, face, and neck injuries are among the most common IPV-related injuries reported. Per the Centers for Disease Control and Prevention, IPV refers to “physical, sexual, or psychological harm by a current or former partner or spouse.” The National Intimate Partner and Sexual Violence Survey indicates that 1 in 4 women in the United States experienced contact sexual violence or physical violence compared with 1 in 10 men.
Brain injuries sustained by women experiencing IPV are unique in that these women are more likely to sustain repetitive injuries—most often caused by blows to the head, neck, or face, with 29% to 39% of women also reporting attempted strangulation, a potential cause of hypoxic-ischemic brain injury. ,
One poorly studied population that appears to be at increased risk for IPV—and thus for IPV-related TBI—is the lesbian, gay, bisexual, and transgender (LGBT) population. Data are currently lacking, but beyond being at increased risk, research has shown that LGBT individuals face additional barriers to seeking treatment that are unique to their sexual orientation or gender identity including fear of outing oneself when seeking help, the lack of LGBT-friendly resources, and potential homophobia from service providers. ,
Sex and gender-based differences regarding IPV-related TBI add complexity to an already understudied topic. Further research is needed to define and address barriers that discourage victims from reporting events and seeking treatment.
Review questions
- 1.
Strengthening of which muscles may decrease incidence of concussion in young athletes?
- a.
Neck
- b.
Temporalis and frontalis
- c.
Deltoids
- d.
Abdominal
- a.
- 2.
When comparing the sexes, which statement is true regarding the incidence of traumatic brain injured (TBI)-related hospitalizations and TBI-related deaths?
- a.
Women have higher rates of TBI-related hospitalizations but a lower incidence of TBI-related deaths.
- b.
Women have lower rates of TBI-related hospitalizations but a higher incidence of TBI-related deaths.
- c.
Women have higher rates of TBI-related hospitalizations but a lower incidence of TBI-related deaths.
- d.
Women have lower rates of TBI-related hospitalizations and a lower incidence of TBI-related deaths.
- a.
- 3.
Administration of progesterone in clinical studies on TBI has consistently shown what effect on outcomes?
- a.
Reduced mortality
- b.
Decreased disability
- c.
Conflicting results
- d.
More adverse events
- a.
Answers on page 401.
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- 4.
The greatest disparity in incidence of TBI in males versus females occurs
- a.
during adolescence.
- b.
<2 years old.
- c.
>65 years old.
- d.
between the ages of 50 to 62.
- a.
- 5.
In terms of incidence of concussion in sports with the same rules for women as for men, women suffer concussions at what rate compared with men?
- a.
Higher incidence than men
- b.
Lower incidence than men
- c.
Equivalent incidence compared with men but with worse outcomes
- d.
Equivalent incidence compared with men but with better outcomes
- a.
- 6.
One explanation for the higher incidence of sports-related concussions in females is because of which bias?
- a.
Hindsight bias
- b.
Confirmation bias
- c.
Reporter bias
- d.
Anchoring bias
- a.
- 7.
How do sports-related concussion outcomes differ for females compared with males?
- a.
Females recover faster but experience more severe and longer-lasting deficits.
- b.
Females take longer to recover and experience more severe and longer-lasting deficits.
- c.
Females take longer to recover but experience less severe deficits.
- d.
Females recover fast and experience less severe and shorter-lasting deficits.
- a.
- 8.
Which of these is true regarding moderate to severe TBI in postmenopausal women versus men?
- a.
They exhibit similar mortality rates as men after sustaining moderate TBI.
- b.
They have reduced mortality but a higher rate of complications.
- c.
They have reduced mortality and fewer complications.
- d.
They exhibit similar mortality rates as men after suffering severe TBI.
- a.
- 9.
Which of these is true regarding intimate partner violence (IPV)-related TBI?
- a.
Are typically singular events caused by direct trauma to the head
- b.
Occur equally between sexes
- c.
Are often repetitive injuries with the possibility of underlying anoxic brain injury caused by strangulation
- d.
Are frequently reported
- a.
- 10.
Longer duration of amenorrhea after TBI has been linked to?
- a.
Decreased mortality
- b.
Decreased morbidity
- c.
Worse outcomes and community participation
- d.
Less severe injuries
- a.
References
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