Published on: November 28, 2015
by Dr. Angela Colantonio & Dr. David Stock for Women’s Brain Health Initiative:
Each week we hear of athletes who suffer concussions or more severe forms of brain injury. Perhaps more troubling are the stories of former athletes with repeated concussions who years later suffer from early onset dementias. Historically, due to the higher numbers of males participating in contact sports, military combat or other higher risk activities, men have been up to three times more likely to experience brain injury.
As a result, the vast majority of research on this topic has been male-focused, leading to potentially important gaps in our understanding of the risk factors and both short and long term outcomes of Traumatic Brain Injury (TBI). For instance, TBI in the context of intimate partner violence, where up to 92% of hits are to the head, has received relatively little attention.
What is TBI?
TBI has been defined as an alteration in brain function, or other evidence of brain pathology caused by an external force. It is caused by a bump, blow, or jolt to the head or by a hit to the body that causes the head and brain to move back and forth rapidly. The severity can range from critical leading to death to mild TBI commonly called concussion.
A concussion, which is the most common form of TBI, may or may not involve a loss of consciousness. You do not have to black out, or be knocked out, to experience a concussion. Concussion may result in an altered mental status that affects cognitive (e.g. thinking, memory, learning) and physical performance. Symptoms after concussion usually resolve within weeks but can persist.
More serious TBI can result in more persistent and serious problems with thinking ability, language/communication, sensation (problems with vision, smell etc). Motor problems can occur which may include muscle weakness and coordination. Also emotional problems are common which can involve problems with mood, impulse control and personality changes. TBI has a very large human and economic impact on society.
What do we know of the key differences in TBI for men and women?
Researchers have observed female rats to be more likely to survive acute head injury and have better immediate outcomes than males. Higher levels of reproductive hormones such as estrogens and progestogens have been implicated in improved outcomes for females (Herson, Koerner et al. 2009). It is surprising, however, that most animal studies on TBI have been done exclusively on male rodents. Current policies by funding agencies internationally are trying to address this gap in both animal and clinical studies.
Differences found in animal studies, however, have not shown consistent results in human studies. The first reviews of clinical studies showed that overall, outcomes were worse for women after TBI (Farace and Alves 2000). However, important factors such as the average age of injury being higher in women, were not taken into account, potentially at least partially explaining this finding.
Women who have sustained a TBI have reported more headaches and dizziness long term than men. A U.S. study from 2007 reported that female high school and college-level athletes are more likely to be concussed (i.e., have a mild TBI) than males, despite being less likely to participate in the highest risk sports such as football (Gessel, Fields et al. 2007).
Some of this might be a result of girls being more inclined to report injury, but differences in musculature may also mean that, on average, girls are less resilient to these injuries when playing high intensity sports. There is mixed evidence in terms of exactly how and why experiences may differ following a TBI among men and women. Physiological factors, such as differences in reproductive hormone or societal influences may affect injury severity and recovery.
The Canadian Institutes for Health Research’s Institute of Gender and Health funded the first comprehensive study on longer-term reproductive outcomes specifically among women with moderate to severe TBI (Colantonio, Mar et al. 2010). Menstrual cycle disruption was reported to occur in the majority of women following TBI and another study reported women to be more likely to suffer more painful periods post injury. Though the effect on conception appears to be minimal, there is indication that women living with the effects of TBI have fewer live births. The long-term impact of reproductive health in women aging with TBI is still not known.
A large clinical study published last December in the New England Journal of Medicine evaluated whether progesterone treatment immediately following TBI was beneficial (Wright, Yeats et al.). Researchers did not find that treatment with progesterone
improved outcomes, but surprisingly, they discovered that women responded significantly worse to the hormone. Further study into why such sex differences exist is vital to a better understanding of how to avoid negative outcomes after TBI, including future risk of cognitive decline and dementia.
The growing evidence indicating that TBI is indeed a risk factor for dementia suggests that at least as much attention should be paid to prevention. The importance of prevention of brain injury cannot be emphasized enough. The main causes of injury are falls, motor vehicle collisions and being struck by an object or person. Further, after a concussion, it is important to rest immediately after the injury and not return to sport or other activity too early to avoid risk of re-injury. For older adults who fall, it is important to rule out brain injury. Cognitive signs from a brain injury could be interpreted as dementia. Protecting your brain from a traumatic brain injury may very well be one way to decrease your risk for dementia.
Signs & symptoms:
Signs & symptoms of a concussion include a new onset of one or more of the following symptoms, but are not limited to:
Some symptoms may not be present immediately after the injury, but may emerge in the subsequent hours or days. It is therefore important to monitor for symptoms several days following a head injury.
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