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The Long-Term Effects of Subtle Brain Injury in Athletes and Military Personnel
January 25, 2025
In the fast-paced world of sports and military service, head impacts are nearly inevitable. Whether it’s the thud of a helmet making contact during a football game, a player heading a soccer ball, or even the jarring force from a baseball bat, these incidents often go unnoticed in the short term. However, the cumulative effect of repeated, seemingly minor head hits may be much more dangerous than previously thought.
As concussion research has evolved, it has led to significant changes in how contact sports are played. Professional athletes follow detailed concussion protocols, and youth athletes are prohibited from heading soccer balls until the age of 11. But what about the repeated, smaller hits to the head? Can these repeated impacts, often without obvious symptoms, cause lasting damage?
Dr. Jeff Bazarian, a leading expert in concussion research at the University of Rochester Medical Center, believes that repeated head hits may be a silent danger. These impacts may not present immediate symptoms, but they can compound over time, leading to subtle neurological changes that affect performance and increase the risk of more serious injury down the road.
Athletes, particularly those in contact sports, and military personnel who face repeated head impacts may experience declines in balance, reaction time, and other cognitive functions. While these changes may not be visible in standard exams, they could impair athletic performance and increase the risk of further injury. Moreover, over time, the cumulative damage could contribute to neurodegenerative diseases, though there is currently no standardized method to track or treat these hits.
“We’re working to understand if we can detect and mitigate the effects of repetitive head impacts on the brain,” says Dr. Bazarian. “Our hope is that this approach will lower the long-term risk of neurodegeneration for those exposed.”
A Multi-Institutional Study
To better understand the effects of repeated head hits, Dr. Bazarian is leading a groundbreaking study that will track college athletes from multiple institutions, including the University of Rochester, University of Buffalo, Indiana University, and The Citadel. Male football players and female soccer players will be monitored as they play, using specialized mouthguards equipped with sensors to track the number, force, and direction of head impacts during practices and games. In addition, blood samples will be taken to analyze brain proteins linked to head hits.
Athletes will also undergo tests before and after games, including:
- Quantitative EEG: Five minutes of brainwave activity measurement.
- Blink Reflex: Testing eye-lid reaction times.
- Hand-Eye Reaction Time: Measuring reflexes and motor coordination.
- Near-Point Convergence: Assessing visual focus during a test of eye function.
Despite not yet being used as diagnostic tools, these tests may reveal subtle abnormalities in athletes who have been exposed to repeated head impacts. These findings will be compared to structural changes in the retina, an area that may show signs of damage linked to head injuries.
Optical Imaging and New Treatment Approaches
One promising technology being used in the study is optical coherence tomography (OCT), which provides detailed, non-invasive images of the retina and optic nerve. Previous research has shown that changes in the retina can be correlated with the number of head hits experienced by athletes, making OCT a valuable tool in identifying brain injury.
At the end of the season, athletes showing signs of neurologic abnormalities will be split into two groups. One group will rest for two weeks, while the other will engage in daily aerobic exercise for 20-30 minutes—current standard care for concussion recovery. Researchers anticipate that those in the exercise group will show greater improvements in brain function.
A key area of research will also focus on whether there is a threshold for the number of head hits an individual can sustain before permanent damage occurs. Researchers at Boston Children’s Hospital will use animal models to investigate this question, aiming to understand the precise limits of brain injury due to head impacts.
The Big Question: How Many Hits Are Too Many?
With ongoing research, scientists hope to identify the threshold beyond which repetitive head hits become harmful. The answer could have significant implications for sports protocols and military safety standards in the future.
Dr. Bazarian’s team is at the forefront of exploring the subtle but dangerous effects of repeated head impacts. Through their multi-pronged approach, they hope to shed light on an area that has long been overlooked in concussion research.
Disclaimer: The information provided in this article is for informational purposes only and should not be construed as medical advice. Consult with a qualified healthcare provider for diagnosis and treatment regarding concussions and head injuries.
