Replacing the term "subconcussive" to improve understanding of brain injuries
By Sneha Bansal. This article was initially published in the 7/25/24 edition of our Concussion Update newsletter; please consider subscribing.
In a recent editorial published in the British Journal of Sports Medicine, a team of experts from Harvard University, Boston University, the Mayo Clinic, and the Concussion Legacy Foundation argue that the term “subconcussive” should be replaced by new terms when referring to head impacts and injuries, specifically subclinical head acceleration events (HAEs) and injuries, “as defined by clinical, biomarker and/or neuroimaging change.” The authors recommend using the more agnostic term “non-concussive” to describe HAEs that do not result in a diagnosed concussion. The term “subconcussive” is a misnomer, as data from helmets and mouthguards has revealed that “many HAEs are associated with greater head acceleration than impacts that result in a diagnosed concussion.”
The authors recommend using “subclinical TBI” instead of “subconcussive injury,” as some non-concussive impacts may still cause injury associated with changes in brain function, biomarkers, and imaging, even in the absence of symptoms. In this case, the term “subconcussive” is contradictory, as it implies no injury occurred. The authors reference studies that show “increasing biomarkers of neuroinflammation” after acute HAE exposure and other studies that show repetitive HAE over time may increase the risk of concussion. They point out that recent studies have also correlated long-term repetitive HAE exposure to neurodegenerative diseases.
Dr. Chris Nowinski, the lead author of the editorial and co-founder and CEO of the Concussion Legacy Foundation (CLF), discusses this issue in a CLF blog post: “Scientists have been referring to head impacts that don’t cause concussion symptoms as ‘subconcussive impacts,’ which implies they are less than concussions. This has even led to CTE experts saying CTE is caused by ‘small, repetitive impacts.’ But when it comes to the size of the hit, 10% of head impacts are more than [the level of HAE that has caused some] concussions. We recommend replacing ‘subconcussive’ with ‘non-concussive’ to better describe these impacts. After a head impact, a concussion was either diagnosed, or it wasn’t.”
By changing the terminology, the authors aim to add specificity and clarity to understanding non-concussive impacts and their potential for causing subclinical brain injury. This argument is an essential step in advancing the conversation around concussions and repetitive head impacts in sports.
See our newsletter synopsis on research concerning long-term repetitive HAE and CTE and our Neurodegenerative Disease resource concerning elevated risk for neurodegenerative disease in former professional Scottish soccer players.
