Dr. Glynnis Zieman Discusses Gender Differences in Brain Injuries
Research has shown that traumatic brain injury incidence, symptoms, and recovery vary between men and women. Barrow Sports Neurology Fellow Glynnis Zieman, MD, discussed differences between the genders that may play a role in the disparity – as well as which female populations have a greater risk for traumatic brain injury. (Watch Dr. Zieman’s talk.)
The Brain Injury Association of America defines traumatic brain injury (TBI) as an alteration in brain function, or other evidence of pathology, caused by an external force. Neurologists usually classify TBI as mild, moderate, or severe using the Glasgow Coma Scale – a scoring system that describes a person’s level of consciousness after TBI.
Most TBIs are mild injuries called concussions. The American Academy of Neurology defines a concussion as a trauma-induced alteration in mental status that may or may not include a loss of consciousness.
“Historically, TBI has been a problem for young males because they engage in high-risk activities, but this is sort of changing,” said Dr. Zieman, who will join the Barrow Concussion and Brain Injury Center as an assistant professor this summer after completing her fellowship.
A meta-analysis performed in 2000 found that TBI incidence was greater among males than females only from puberty to middle age. A 2007 study showed that female incidence actually exceeded male incidence in older adults, beginning in the 65 to 70 age range.
“But even in that young group where males outnumber the females, that disparity is changing,” Dr. Zieman said. “Title IX was part of the Equality in Education Act in 1972, and that’s basically allowing more women to play sports. There are also more women in the military.”
She discussed several differences between men and women that may play a role in TBI, including stature, hormones, and comorbidities.
Men – on average – weigh about 15 percent more than women. They also tend to have larger heads and brains, greater neck strength, and wider neck girth than women. In other words, men usually have more mass.
“When a force is exerted on someone, if the mass goes down, the acceleration has to go up,” Dr. Zieman said. “So then there’s more of a displacement of the head, and that potentially could lead to high risk of concussions.”
The Role of Hormones in Concussion
Men and women produce the same hormones, but the concentrations differ significantly between the sexes. Hormones are not only actively involved in puberty but also in brain and fetal development.
“For a long time, there have been some known neuroprotective effects with certain hormones,” Dr. Zieman said. “Hormones are involved in a lot of different types of neurological disease, certainly not just TBI.”
Some research suggests that estrogen and progesterone may have neuroprotective effects, but other studies have shown conflicting results.
Comorbid Conditions and Concussion
Comorbidities such as migraine and neuropsychiatric disorders have also been studied in the context of TBI. Women tend to be at higher risk for major depressive disorder and anxiety.
“This weighs in quite a bit with TBI because we know there’s a statistically significant prolonged recovery in people who already have a psychiatric comorbidity to begin with,” Dr. Zieman said.
The Effects of Migraine and the Menstrual Cycle
History of migraine is believed to be a risk factor for prolonged recovery from TBI. About 38 million people in the United States suffer from migraine headaches. Of those 38 million, 28 million are female, according to the Migraine Research Foundation. The prevalence of migraine in children is equal among the sexes until puberty, when female predominance becomes clear.
There are known hormonal effects associated with migraine, particularly a well-established link between migraines and estrogen. A 2004 study found higher incidence of migraine during menstruation, when estrogen levels decrease, and a lower incidence during pregnancy, when estrogen levels are higher.
Many symptoms associated with the menstrual cycle and premenstrual syndrome mimic the symptoms associated with concussion. As such, concussion may lead to the amplification of these symptoms.
In a 2006 study, 76 percent of the women evaluated had at least one baseline symptom, compared with 68 percent of the men. Several of the baseline symptoms, which are symptoms that are present before a TBI, identified in women in this study were symptoms often associated with the menstrual cycle.
More Female Athletes, More Concussions Among Women
Dr. Zieman also discussed special female populations with an increased risk for TBI, including female athletes. Research has shown that female athletes are more likely to sustain concussions than male athletes participating in comparable sports. Dr. Zieman reiterated that this may be due to differences in stature and comorbidties, but she added that reporting bias may also contribute.
“Women are more likely to report their symptoms and seek medical care for them, so that’s probably part of the reason for the disparity,” Dr. Zieman said.
The increased rate may also be due in part to Title IX. According to the National Collegiate Athletic Association, the number of female athletes increased by 80 percent from 1998 to 2004, compared to a 20 percent increase in male athletes.
Concussions Among Elderly Women
Elderly women also appear to be at higher risk than other groups. After age 70, the male incidence lowers and the female incidence increases, according to a 2007 study. However, this could be partially explained by the fact that women tend to live longer than men.
Falls are the leading cause of TBI in the elderly population, and they are more likely to occur in people who live alone, such as widows. Elderly people are also more likely to have a comorbid medical disease, such as dementia or a mild cognitive impairment, which can increase the risk for falls and prolong TBI recovery.
Domestic Violence and Concussions
While both men and women are victims of domestic violence, the National Coalition Against Domestic Violence estimated in 2015 that 76 percent of the 10 million people who are victims each year are women. Domestic violence is described as physical violence by another member of the household, not necessarily by an intimate partner.
“Domestic violence is the leading cause of injury to women, so this is way more common than people realize,” Dr. Zieman said.
She noted that it is a difficult population to study because victims are often hesitant to disclose their injuries for many reasons, including safety concerns. Even when victims do seek help, an estimated 72 percent are not recognized by medical personnel as domestic violence victims.
“Why it’s important for us as a neuroscience community is head, face, and neck injuries are among the most common inflicted by abusers,” Dr. Zieman said.