CHICAGO – A groundbreaking study has revealed that the brain’s waste-clearing system, known as the glymphatic system, significantly declines in function with repeated head impacts. This research, focusing on cognitively impaired professional boxers and mixed martial arts fighters, will be presented at the upcoming annual meeting of the Radiological Society of North America (RSNA).
Sports-related traumatic brain injuries contribute to up to 30% of all brain injury cases, with boxing and mixed martial arts being major contributors. Repeated head impacts are known risk factors for neurodegenerative and neuropsychiatric disorders, making this study particularly relevant.
Understanding the Glymphatic System
The glymphatic system consists of fluid-filled channels that play a crucial role in clearing waste products from the brain, akin to the lymphatic system in other parts of the body. “The recently discovered glymphatic system is like the brain’s plumbing and garbage disposal system,” explained Dr. Dhanush Amin, lead author of the study conducted by researchers from the University of Alabama at Birmingham and Cleveland Clinic Nevada. “It’s vital for helping the brain flush out metabolites and toxins.”
Using diffusion tensor imaging along the perivascular space (DTI-ALPS), a specialized MRI technique, researchers assessed water movement in and around the glymphatic system’s channels. These pathways are essential for regulating fluid balance, transporting nutrients and immune cells, and protecting the brain from damage.
The Role of DTI-ALPS Index
The DTI-derived ALPS index serves as a non-invasive biomarker for assessing glymphatic function. An impaired index can indicate cognitive decline and is linked to conditions like Alzheimer’s and Parkinson’s disease. “When this system doesn’t work properly, damaging proteins can accumulate, which have been linked to Alzheimer’s and other forms of dementia,” noted Dr. Amin, now an assistant professor of neuroradiology at the University of Arkansas for Medical Sciences.
Study Findings and Implications
The researchers analyzed baseline data from Cleveland Clinic’s Professional Athletes Brain Health Study (PABHS), which follows approximately 900 active fighters, including 300 professionals monitored for over three years. The study included data from 280 fighters, 95 of whom were cognitively impaired at baseline, and 20 healthy controls.
Using the DTI-ALPS method, the team assessed glymphatic activity over time and its correlation with the number of knockouts experienced. They also measured differences in glymphatic activity between cognitively impaired and non-impaired athletes.
“We thought repeated head impacts would cause lower ALPS in cognitively impaired fighters compared to non-impaired fighters,” Dr. Amin said. “We also expected the ALPS measurement to be significantly correlated with the total number of knockouts in the impaired fighters.”
Contrary to their hypothesis, researchers observed a significantly higher glymphatic index among impaired fighters, which deteriorated over time with the total number of knockouts. In athletes with continued trauma, glymphatic function significantly declined.
Unexpected Outcomes and Expert Insights
“We believe that the glymphatic index was initially high in the impaired athlete group because the brain initially responds to repeated head injuries by ramping up its cleaning mechanism, but eventually, it becomes overwhelmed,” Dr. Amin explained. “After a certain point, the brain just gives up.” Non-impaired fighters had a significantly lower right and total glymphatic index compared to impaired fighters, highlighting the complex relationship between head trauma and brain health.
Understanding the impact of repeated head impacts on the glymphatic system is crucial for early detection and management of neurodegenerative risks in athletes participating in contact sports. “If we can spot glymphatic changes in the fighters before they develop symptoms, then we might be able to recommend rest or medical care or help them make career decisions to protect their future brain health,” Dr. Amin emphasized.
Looking Forward: Potential for Early Intervention
The study’s findings open new avenues for understanding and potentially mitigating the long-term impacts of combat sports on brain health. With further research, there is hope that early intervention strategies can be developed to protect athletes from the debilitating effects of repeated head trauma.
Co-authors of the study include Gaurav Nitin Rathi, M.S., Charles Bernick, M.D., and Virendra Mishra, Ph.D. As the scientific community continues to explore the glymphatic system’s role in brain health, these insights could lead to significant advancements in the prevention and treatment of sports-related brain injuries.
