Sub-Concussions: A Threat to Brain Health

In 2002, Jeff Astle passed away at the age of 59 after suffering years of slowly declining mental health. Astle was a professional English soccer player in the 1960s and 70s. Prior to his death, doctors and family members thought he was suffering from early-onset Alzheimer’s disease, but the coroner found a different cause of death – chronic traumatic encephalopathy (CTE). Astle’s death raised many questions. CTE is most commonly associated with high-contact sports, such as football or boxing, where serious head traumas and concussions occur frequently. How could someone without a history of concussions or major head injuries die from a disease like CTE? Nicknamed “The King,” Astle was a prolific player known for his skill at heading the soccer ball. Could years of heading the ball be to blame?

Since 2002, concussions have quickly risen to the forefront of sports research. Gone are the days when a severe blow to the head during a football game could be brushed off as part of the game. With an expanding pool of knowledge and research, concussions are now considered a major public health issue.

But what about cases like Jeff Astle’s? What about when doctors find posthumous brain injuries in people who haven’t had a series of concussions? As more and more professional athletes are diagnosed with neurodegenerative diseases, the long-term consequences of repeated head impacts are becoming clearer.

Recent findings indicate that a newly identified threat, called sub-concussive head impacts, may be doing more damage than previously thought. Researchers are finding positive correlations between CTE and the amount of time spent playing sports with long-term exposure to sub-clinical head trauma. “This indicates that the cumulative head impacts or sub-concussive hits may be more important than concussions” says Peter Kiernan, a research assistant at Boston University’s CTE Center, which performed the definitive studies on CTE.

A doctor can diagnose a concussion based on any number of symptoms that appear as a result of an impact to the head. Symptoms may include headaches, vision problems, balance issues, as well as possible changes in hearing, speech, or smell. Sub-concussions differ in that they do not present any signs or symptoms. Doctors define a sub-concussive impact as any impact or force to the head that does not result in a concussion diagnosis. Yet sub-concussions may have major consequences. Anthony Petraglia, a neurosurgeon at Rochester Regional Health, NY, and expert in sports related neurological injuries says, “This concept of sub-concussion is a significant emerging one that definitely requires thorough consideration.”

Several studies show that athletes at college, high school, and youth levels can sustain anywhere from several hundred to over a thousand head impacts during a single season of football. A 2016 study out of Wake Forest School of Medicine examined structural changes in the brains of 25 youth football players (ages 8-13) following a full season. Researchers performed brain imaging scans prior to the start of season and after the season ended. The scientists kept detailed data measuring both number and severity of head impacts for each individual player. They only measured sub-concussive events; if a player sustained a concussion, the researchers excluded him from the study. At the conclusion of the football season, researchers found a significant relationship between the number and severity of head impacts and structural changes in certain areas of the athletes’ brains. For these participants, stronger and more frequent head impacts corresponded with larger physical brain changes.