Repetitive hits to the head, not just concussions, during a professional football career are associated with a statistically significant and substantially increased risk for death, a new study suggests.
“We found that increasing head impacts, not just concussions, increased the risk for mortality among NFL players,” study investigator Brittany Kmush, PhD, Syracuse University, in New York, said in a statement.
“The association persisted even when allowing for the healthy worker effect to provide a conservative estimate of the association of head impacts with death. Rule or equipment changes that minimize repetitive head impacts may lower the risk of mortality,” Kmush told Medscape Medical News.
The study was published online May 11 in JAMA Network Open.
Twofold Increased Risk
The researchers conducted a retrospective cohort study of 14,366 National Football League (NFL) players who played between 1969 and 2017. The mean age of the players was 47.3 years, and the mean body mass index (BMI) was 29.6. Overall, 763 players (5.3%) had died.
In their assessment, the investigators used the Association of Professional Football Cumulative Head Impact Index (pfCHII), which considers the amount of time that a player is at risk (number of games and practices over their career, as available in the Pro Football Reference), and position risk adjustment, derived from studies using helmet accelerometer data.
The pfCHII has been validated as a predictor of later-life neurobehavioral and cognitive impairment in NFL players. The design of the current study “minimized the selection and recall biases found in previous studies among NFL players,” Kmush said.
Among the 13,912 players included in the main analysis, the median pfCHII score was 32.63 (interquartile range, 13.71 – 66.12). The quarterback and wide receiver positions were associated with lower scores, and the linebacker, defensive back, and offensive/defensive lineman positions were associated with higher scores.
After adjusting for birth year, BMI, and height, a 1-log increase in pfCHII was associated with a twofold increased risk for death (hazard ratio, 2.02; 95% confidence interval, 1.21 – 3.37; P = .01) for seasons 1969 to 2017.
“To increase the pfCHII by 1%, a player with 1 season of practices would need to play only 1 additional game the next season. To increase the pfCHII by 25%, a 1-season player would need to add only half of a regular season of game play and practice time the next season,” the researchers write.
In all models, increasing BMI was statistically significantly associated with increased risk for death, a finding that is consistent with previous studies.
“The results of this study suggest that efforts by policy makers to directly reduce repetitive head impacts may be beneficial to football player health,” the investigators note.
“Policies consistent with this objective are being piloted in the National Collegiate Athletic Association and NFL but should also be implemented for high school and youth leagues,” they suggest.
Need for Prospective Research
Commenting on the findings for Medscape Medical News, Jamie Ullman, MD, director of neurotrauma, North Shore University Hospital, Manhasset, New York, said the study is “very interesting, and the authors have done a tremendous job in working with data compiled from the readily available Pro Football Reference.”
Ullman noted that although other studies have suggested that repetitive head injury is potentially associated with long-term problems among NFL players, Kmush and colleagues used increased time of exposure to potential head injury and players’ field position as a way of suggesting a higher risk for death.
“The number of actual impacts to the head can only be surmised from these data, and the retrospective nature of this study cannot be overlooked,” he cautioned.
“We are in need of seeing rigorous, long-term, prospective studies in large numbers of professional athletes that include biomechanical data in addition to physical, serum, radiographic, and cognitive testing, to name a few, so that we can more accurately assess the morbidity and mortality risks for these players,” Ullman said.
The study was supported by funds from the David B. Falk College of Sport and Human Dynamics, Syracuse University. Kmush and Ullman have disclosed no relevant financial relationships.
JAMA Netw Open. Published online May 11, 2020. Full text