# Can Repeated Concussions Accelerate Alzheimer’s Disease?
The connection between head injuries and brain disease has become increasingly clear through scientific research. Former NFL players show a significantly higher risk of developing Alzheimer’s disease and other neurodegenerative conditions compared to the general population. A study of more than 3,400 long-term NFL players found that the risk of death from neurodegenerative disease was triple that seen in the general population, with the risk of death from Alzheimer’s or ALS being nearly four times higher among former players.
Understanding how this happens requires looking at what occurs in the brain after injury. When a traumatic brain injury occurs, even a mild one, it triggers harmful changes in the brain. Researchers at the University of Virginia discovered that traumatic brain injuries impair the function of lymphatic vessels that connect the brain and the immune system. These vessels, located in the brain’s protective membranes, play a vital role in cleaning and protecting the brain. When they don’t work properly, the brain cannot clear out harmful substances as effectively.
One of the most damaging substances that accumulates after brain injury is a protein called tau. Normally, tau helps stabilize structures within brain cells called microtubules. However, when tau accumulates abnormally, it forms tangles that cluster around blood vessels and spread throughout the brain, disrupting how neurons function. This same tau buildup is a hallmark of Alzheimer’s disease. Research shows that traumatic brain injury accelerates the accumulation of this harmful tau protein, which means a single mild brain injury can set off changes that increase the risk of Alzheimer’s disease developing later in life.
The damage from repeated head trauma appears to be particularly concerning. Experts believe that repeated impacts to the head, neck, and back cause cumulative damage that leads to a breakdown and buildup of tau protein in the brain. More severe blows to the head can be potentially more problematic, especially if adequate time for recovery between concussions does not occur. Repeated concussions, particularly those that do not allow sufficient recovery time before another occurs, are considered one of the hypothesized mechanisms for developing chronic traumatic encephalopathy, or CTE, a progressive brain disease with features of Alzheimer’s, ALS, and Parkinson’s disease.
The research also reveals that traumatic brain injury has been linked to multiple other neurodegenerative disorders beyond Alzheimer’s, including ALS, Parkinson’s disease, and CTE. Scientists have identified specific effects caused by mild traumatic brain injury, including harmful changes to immune cells called macrophages that normally act as brain defenders and debris removers.
It is important to note that while the evidence strongly suggests a connection between head trauma and neurodegenerative disease, researchers emphasize that no single study can make a definitive conclusion about whether concussions directly cause these diseases. The body of scientific literature as a whole is what matters most. Additionally, concussion histories in many studies are unknown, raising the possibility that factors other than head trauma might also be at play. However, preventing concussions remains a logical step to take given the potential risks.
The median age of death from all causes among the NFL players studied was 54 years old, suggesting that these neurodegenerative diseases may develop and progress more rapidly in those with repeated head trauma. This underscores the importance of head injury prevention in contact sports and other activities where head trauma is a risk.
Sources
https://www.eurekalert.org/news-releases/1109997
https://news.umiamihealth.org/en/cte-the-hidden-brain-risks-beyond-football/
