Prior head injury is associated with a 34% increased risk of stroke in older adults (6/27/24 Newsletter)
This week’s lead article, Prior head injury is associated with a 34% increased risk of stroke in older adults is in the Statistics category.
In addition to the usual synopses, this newsletter features our impact report, a spotlight on Concussion Alliance resource pages, and a popular newsletter synopsis from our Archives.
In this newsletter: Opportunities, Veterans & Service Members, Statistics, Women’s Health, Archives Highlight, Impact Report, and Pertinent Concussion Alliance Resources.
We appreciate the Concussion Alliance volunteers and staff members who created this edition:
Writers: Kaori Hirano, Sravya Valiveti, Esmeralda Garcia-Ramirez, and Malayka Gormally.
Editors: Conor Gormally and Malayka Gormally
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Opportunities
Summer learning: There are few live webinars during the summer, so we recommend checking out the recordings of this past season’s webinars produced by the University of Michigan Concussion Center, the Canadian Concussion Centre, the Center on Brain Injury Research and Training, and the International Brain Injury Association.
Participate in concussion research: Researchers at the University of Colorado invite you and a significant other (friend, partner, family member, etc.) to participate in an online study assessing neuropsychological symptoms that may be linked to your concussion history. See our blog post for information on how to enroll.
Participate in CTE research: researchers are recruiting for the BANK CTE study to “see if blood can be used to detect CTE. Once CTE can be diagnosed in life, then researchers can explore treatments, and hopefully a cure.”
Veterans & Service Members
Blast mTBI is associated with impaired function of the glymphatic system. Sleep quality is also a factor–Interventions to improve sleep may help
Veterans exposed to blast-induced mild traumatic brain injury (blast mTBI) may experience impaired function of the glymphatic system, according to a recent study published in Brain. (Blast mTBIs are “caused by exposure to a pressure wave from an explosion.”) In the first two parts of this three-part study, the brain tissue of veterans exposed to blast mTBI and the brains of mice who were exposed to similar blasts had abnormal expressions of aquaporin-4 (AQP4), a key part of the glymphatic system, which is responsible for clearing waste from the brain. In the clinical MRI section of the study, veterans exposed to blast mTBI showed signs of glymphatic dysfunction.
Molly Braun et al. concluded that exposure to blast TBI—which nearly half of the injured service members in the Iraq conflict experienced—may cause changes in AQP4, leading to dysfunction in the glymphatic system. The build-up of waste products in the brain is one factor in the development of neurodegenerative diseases such as Alzheimer’s and chronic traumatic encephalopathy (CTE). The authors also posit that glymphatic dysfunction may underly common comorbidities such as depression and post-traumatic stress disorder.
Additionally, higher glymphatic dysfunction in living veterans “may contribute to the development and persistence” of post-concussion symptoms. The study found that glymphatic dysfunction was “associated with the persistence of a wide range of post-concussive symptoms,” with these symptoms lasting, on average, 4-5 years after an individual’s last blast mTBI. They also found that poor sleep appears to worsen glymphatic function in those exposed to blast mTBI, so therapeutic sleep interventions may improve glymphatic function and symptom outcomes for these patients.
Braun et al.’s study consisted of three main components. The first part of the study examined how much and where APQ4 appeared in the brain tissue of deceased veterans who had experienced blast TBI. Compared to the brains of veterans with no exposure to blast TBI, veterans with blast TBI history had abnormal expression of AQP4. To test whether these changes in AQP4 were associated with glymphatic system dysfunction, the researchers exposed mice to repetitive blast mTBI to mimic what veterans had experienced. In blast-exposed mice, AQP4 changes similar to those of humans were observed. The mice with abnormal AQP4 expression also had impaired glymphatic function. Finally, the study used neuroimaging to examine the perivascular spaces in the veterans’ donated brain tissue. Perivascular spaces are fluid-filled spaces around blood vessels that are part of the glymphatic system. The authors found a higher number of enlarged perivascular spaces, indicating glymphatic dysfunction, in veterans exposed to blast TBI.
Braun et al.’s findings illustrate the impacts of blast TBI on the glymphatic system, which can have long-lasting effects on brain and psychological health in veterans. Prior research has linked impaired functioning of the glymphatic system to increases in amyloid beta and tau proteins, both of which are associated with CTE and Alzheimer’s Disease. Still, further research is required to fully understand the relationship that AQP4 and the glymphatic system have on outcomes after blast mTBI––with respect to both persisting symptoms and long-run neurodegenerative disease.
Statistics
Prior head injury is associated with a 34% increased risk of stroke in older adults
A press release from Penn Medicine News highlighted that individuals with a history of traumatic brain injury (TBI) were at higher risk of developing an ischemic stroke later in life. Ischemic stroke is a type of stroke that is characterized by a blood clot in the brain. This new research, published in Stroke, evaluated data over 30 years for 13,000 adults and showed that those with prior head injury were overall 34% more likely to have a stroke than those who never suffered a brain injury. At baseline, the study participants were a median of 54 years old, had no history of TBI or stroke, and none were in hospitals or nursing homes at the follow-up (a median of 27 years later). Head injuries varied in severity, from mild concussions to skull fractures and other head trauma. Holly Elser et al. found that there was a dose-response relationship; those with one head injury had a 16% increased risk of stroke, while those with two or more head injuries had a 94% increased risk of having an ischemic stroke. The research team also found that the head injury severity did not influence the increased risk of stroke, but multiple head injuries showed a strong association with more severe stroke later in life.
It is worth noting that these new findings shed light on the relationship between brain injury and its long-term impacts on brain health and stroke risk later in life, which adds to other recent research that also found associations between brain injury and other long-term conditions such as dementia and late-onset epilepsy, as well as disability status. This establishes a need for early intervention in those who are at higher risk of stroke due to a history of head injury alone. The lead author, Holly Elser, a Neurology resident at Penn Medicine, stated that clinicians should counsel those patients who are at higher risk on lifestyle changes and measures that can help patients monitor the risk and manage the risk factors associated with a stroke such as high blood pressure and high cholesterol. She also called for better prevention and safety measures, such as wearing bike helmets and seatbelts that protect against more severe brain injury to hopefully mitigate the long-term risk of developing future conditions associated with brain injury.
Women’s Health
Understanding sex differences in concussion: female vulnerability in concussions
A study published in Acta Neuropathologica found that female swine brains are at a "higher risk of concussion and suffer worse outcomes" than male swine brains. Researchers Hailong Song et al. made this finding based on 16 "clinically relevant swine models" aged approximately 6-8 months, who were given experimental concussions to explore the differences between the sexes in terms of axonal injury. It is worth mentioning that the study only focuses on one area of the brain, the white matter, because damage to axonal fibers in the white matter has been increasingly recognized as a key pathological basis of concussion.
The findings revealed significant structural differences based on staining techniques such as immunohistochemical, immunofluorescent, and transmission electron microscopy. Compared to males, females suffered more swollen axons 24 hours after the concussion and a more widespread loss of axonal sodium channels. Sodium channels are important to the brain because they help with axonal signaling; a concussion disrupts the brain's signaling. Also, concussions selectively result in the loss of smaller diameter axons, and females have a higher proportion of smaller axons, which previous research has revealed. These smaller diameter axons are more vulnerable to traumatic brain injuries. This research study highlights the need for various sex-specific approaches in treating and understanding concussions and other traumatic brain injuries.
In a press release from Penn Today, senior author Douglas Smith says that understanding sex-specific differences in brain structures supports the use of known biomarkers (such as axon protein fragments) to develop ways to measure injury severity, monitor recovery, and develop new treatments. Understanding sex-based structural differences would also offer insight into how other brain conditions can affect the axons, such as Alzheimer's and Parkinson's. These new findings may reveal some insight for future studies into whether females are more vulnerable to neurodegeneration.
From the Archives
Continuing debate about helmets in girls’ lacrosse
Blog post from April 2022
As described in an article by Tom Dart in The Guardian, the use of helmets in women’s lacrosse continues to be a topic of significant debate, as helmets are not mandatory in women’s lacrosse but are required in men’s lacrosse. A 2015 study found that women’s lacrosse had the second-highest rate of concussions among a variety of high school and college sports, including soccer, football, and hockey.
Concussions have long-term effects that impact many women in lacrosse. Becca Losch, for example, suffered a concussion after a blow in the back of her head during a pre-game warmup drill. After her injury, her health diminished greatly; she was unable to complete daily tasks and attend school due to migraines and an inability to focus, among other symptoms. Ten years later, she still receives botox injections to treat her migraines.
Unfortunately, over 72% of concussions in women’s lacrosse are attributed to stick or ball contact head injuries, many of which could have been prevented by wearing the same helmets worn in men’s lacrosse, as shown in a study published in 2020. Concussion Alliance would like to note that while helmets help reduce the risk of concussion through padding and distribution of force, they do not prevent all concussions.
Florida began requiring helmets for all women’s high school lacrosse teams in 2015. Still, seven years later, Florida remains the only state that has mandated helmets for women’s lacrosse, even though a 2021 study demonstrated the reduced incidence of concussions in lacrosse in Florida relative to other states without a helmet mandate.
The resistance to the helmet requirement in women’s lacrosse is also evident in USA Lacrosse, the governing organization of lacrosse in the United States. Ann Kitt Carpenetti, the Vice President of the organization, has yet to support the widespread mandating of helmets in women’s lacrosse. She notes that there is insufficient evidence to require helmets for all women in the sport.
Concussion Alliance recommends checking out the Brain Safety Alliance, which advocates for headgear for Women’s Lacrosse.
Check out our impact report!
We made transformative progress with Concussion Alliance and the communities we serve over the past twelve months. Please take a look at our Spring Impact Report to read stories of the impacts your donations make possible.
Concussion Alliance resources related to the research studies in this newsletter
Concussion in Women and Girls
Our Concussion in Women and Girls resource covers symptoms, diagnosis and outcomes, pathophysiology differences, TBI caused by intimate partner violence, women in college, mental health considerations, the burden of caretaking, and more.
Resources for Service Members and Veterans
We have a group of resources for service members and veterans. Our index page lists all our separate resource pages, which include governmental treatment centers for mTBI, free non-governmental treatment centers for mTBI, opportunities to participate in remote studies for mTBI treatments, mental health treatment clinics (VA and free nonprofit clinics), self-care apps for mental health/PTSD/mTBI, and more.
Concussion in Youth Sports
Our Concussion in Youth Sports resource provides information about concussion education for youth athletes/coaches/parents, the benefits of youth sports, myth-busting, signs and symptoms of concussion, subconcussive hits, multiple concussions, the impact of sex on concussion risk and outcomes, return to learn, return to play, preventative measures, and specific information for players and coaches.
Neurodegenerative Diseases
Our Neurodegenerative Diseases resource provides information on concussions and repetitive subconcussive impacts and their relationship to neurodegenerative diseases, including Chronic Traumatic Encephalopathy (CTE), dementia and Alzheimer's, Parkinson’s disease (PD), and Amyotrophic Lateral Sclerosis (ALS).