Thanks to Dr. Bennet Omalu and researchers like Boston University’s Ann McKee we now understand that repeated concussions lead to chronic traumatic encephalopathy (CTE), an irreversible neurodegenerative disorder that can include behavior and mood problems, memory loss and even dementia.
But what about repeated blows to the head that do not result in concussions, but rather resemble “getting your bell rung”? In a recent paper, researchers from Syracuse University show even repeated head impacts that do not result in concussions can lead to CTE and premature death.
For their study, the research team led by Brittany Kmush, professor of public health at Syracuse, studied nearly 14,000 NFL players from 1969 to 2017. To understand exposure, the team created a “professional football cumulative head impact index” (pfCHII) that combined padded practice time and games played as a professional. To account for a player's position, Kmush and team used a player position risk adjustment based on helmet accelerometer studies developed by Boston University's Alzheimer's Disease and CTE Center. The study adjusted for birth year, body mass index and height.
According to the study results, an NFL player who plays 24 games (a season and a half) increases the pfCHII by 25 percent—thereby increasingly the likelihood of premature death by 16 percent. A 100 percent increase in pfCHII was associated with a 56 percent increase in the risk of death. Additionally, consistent with previous studies, a higher BMI was significantly associated with increased risk of death.
The study also revealed offensive linemen are at the highest risk of repeated head impacts and increased risk of death. By definition, the pfCHII is associated with length of exposure and position—the higher the median pfCHII, the higher the risk of death. Offensive linemen had a median pfCHII of 84, followed by defensive linemen at 66, and linebackers at 54. The remaining positions saw a large drop-off: defensive backs at 29, running backs at 23, wide receivers at 14 and quarterbacks at 15.
It’s vital to note the pfCHII does not include college, high school or youth exposures to head impacts. In many cases, by time a player makes it to the NFL, he has already had multiple untreated concussions and severe head impacts.
The researchers plan to expand upon their study by further validating the pfCHII using film-based correlation and clinical studies.
“The pfCHII could also be used to identify practices and on-field playing characteristics that put certain players or positions at a high risk of increased exposure to repetitive head impacts,” they write in their paper, published in the Journal of the American Medical Association.
Based on their findings, the Syracuse team believes a reduction in repetitive head impacts through additional rule and equipment changes may be associated with reduced mortality.
“Traditionally, federal agencies such as the Occupational Safety and Health Administration have allowed leagues to self-regulate the health and safety of players, with exceptional cases being governed largely by tort law. Given recent research findings regarding public health issues raised by contact sport participation, this may not be an optimal approach within the modern landscape,” Kmush and team conclude.