February 22, 2024

Longer football careers linked to reduced integrity of the brain’s white matter, research shows

Have you ever wondered how playing football affects the brain in the long term? A study from the Boston University Chronic Traumatic Encephalopathy (CTE) Center has shed new light on this question, showing that long careers in American football are linked to changes in the brain’s white matter. These changes are associated with cognitive and behavioral problems later in life, independent of the presence of CTE, a condition often highlighted in discussions about the risks of contact sports.

The findings were published in Brain communication.

The motivation behind this extensive research was growing concern about the long-term effects of repetitive head impacts experienced by football players. Previous research has linked these consequences to symptomatic concussions, as well as the development of CTE, a progressive brain disorder.

However, there was a gap in understanding how repeated head impacts affect the brain’s white matter, crucial for cognitive function and behavioral regulation. This study aimed to bridge this gap by examining the relationship between the length of a football career, the age at which players start playing tackle football and changes in the white matter of the brain.

To conduct this study, researchers analyzed brain tissue from 205 male former American football players who had donated their brains to the Veterans Affairs-Boston University-Concussion Legacy Foundation Brain Bank. These individuals had played football at various levels, from youth leagues to professionals.

The study focused on measuring the levels of myelin-associated glycoprotein and proteolipid protein 1 in frontal cortex tissue. These proteins are essential for the structure and function of myelin, the protective sheath around nerve fibers that speeds electrical signals between brain cells.

Neuron, nerve cell axon, and myelin sheath substance surrounding the axon.

Lower levels of these proteins indicate compromised white matter integrity. White matter consists of nerve fibers that connect different parts of the brain, facilitating communication between them. White matter integrity is vital for cognitive functions and behavioral regulation.

The researchers also collected retrospective information on the players’ athletic and medical histories and conducted interviews with family members to collect data on cognitive and behavioral symptoms.

The length of a player’s career played a crucial role in brain health, as more years of playing football were associated with lower levels of proteolipid protein 1. This finding indicates a dose-response relationship between the duration of exposure to repetitive head impacts and the integrity of the brain’s white matter. Surprisingly, this association was not observed with myelin-associated glycoprotein levels, indicating that different components of the myelin sheath may be differentially affected by repeated head impacts.

“White matter damage may help explain why football players are more likely to develop cognitive and behavioral problems later in life, even in the absence of CTE,” said corresponding author Thor Stein, a neuropathologist at VA Boston Healthcare System and assistant professor of healthcare . pathology and laboratory medicine at Boston University Chobanian & Avedisian School of Medicine.

Another important aspect of the study was the impact of the age at which players first started playing tackle football. Beginning at a younger age was associated with lower levels of proteolipid protein 1, suggesting that early exposure to head impacts could disrupt normal white matter development.

This is especially concerning because myelination, the process of forming myelin sheaths around nerve fibers, continues into early adulthood. Therefore, repeated head impacts during critical periods of brain development can have long-lasting effects on brain health.

Among the older brain donors studied, reduced levels of myelin-associated proteins were correlated with greater reported functional and impulse control problems, underscoring the potential role of myelin degeneration in the cognitive and behavioral symptoms observed in individuals exposed to repetitive head impacts. This link between reduced white matter integrity and clinical symptoms highlights the broader impact of football on brain health, beyond the risk of developing CTE.

“These results suggest that existing tests that measure white matter injury during life, including imaging and blood tests, may help elucidate possible causes of changes in behavior and cognition in former contact athletes. We can also use these tests to better understand how repeated blows to the head from football and other sports lead to long-term white matter injury,” said co-author Michael L. Alosco, associate professor of neurology.

However, the research is not without limitations. The sample consisted of brain donors who were symptomatic and had decided to donate their brains for research, which may not represent the broader population of former footballers. Furthermore, the focus on myelin-associated glycoprotein and proteolipid protein 1 measurements in the frontal cortex means that the findings may not apply to other brain areas. Future research will need to include a more diverse group of participants and examine other parts of the brain to fully understand the impact of repeated head impacts.

“More years of playing football and a younger age of first exposure to football were associated with reduced myelin proteins,” the researchers concluded. “… Myelin degeneration is another potential pathological consequence of [repetitive head impacts] which could contribute to the manifestation of clinical symptoms. Further characterization of the pathologies arising from [repetitive head impacts]including those of the white matter, and their relative contributions to objectively defined clinical and cognitive symptoms will inform future iterations of the diagnostic research criteria for traumatic encephalopathy syndrome, as well as treatment and preventive goals in this vulnerable population.

The study, “Reduced myelin proteins in brain donors exposed to football-related repetitive head impacts,” was authored by Michael L. Alosco, Monica Ly, Sydney Mosaheb, Nicole Saltiel, Madeline Uretsky, Yorghos Tripodis, Brett Martin, Joseph Palmisano, Lisa Delano-Wood , Mark W. Bondi, Gaoyuan Meng, Weiming , Victor E. Alvarez, Jesse Mez, Bertrand Russell Huber and Ann C. McKee, and Thor D. Stein.

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