Repetitive Head Impacts Linked to Early Mortality Increase in NFL Players
MAY 13, 2020
Brittany L. Kmush, PhD
A team, led by Brittany L. Kmush, PhD, Department of Public Health, Syracuse University, examined whether repetitive head injuries during a professional football player’s career is linked to an increased risk of all-cause mortality.
In the retrospective cohort study, the investigators examined 14,366 NFL players who played between 1969-2017. The team included all-cause mortality up until July 1, 2018. The investigators excluded 454 special teams players from the final analysis and players with missing data.
The main exposure was a professional football cumulative head impact index (pfCHII), which was measured by combing cumulative padded practice time and games played summed during seasons of play, as well as the player positive risk adjustment from helmet accelerometer studies.
However, only exposure from professional football was calculated and not potential head impacts from college or youth sports.
The investigators used Cox proportional hazards regression to compared hazard ratios (HR) of death by repetitive head impacts. Analyses were also unadjusted and adjusted for birth year, body mass index (BMI), and height.
The mean age of the patient population was 47.3 years old, with the mean BMI of 29.6. Overall, 763 players (5.3%) had died.
Among the 13,912 players included in the pfCHII analysis, the median score was 32.63 (interquartile range, 13.71-66.12). A 1-log increase in pfCHII was linked to significant increases in hazard of death for the 1969-2017 seasons (HR, 2.02; 95% CI, 1.21-3.37; P = 0.01) after adjustment.
The quadratic pfCHII was also statistically significant (HR, 0.91; 95% CI, 0.85-0.98; P = 0.01).
This indicates the hazard of death increased at a decreasing rate while the pfCHII increased.
“The findings suggest that an increase in repetitive head impacts is associated with an increased hazard of death among NFL players,” the authors wrote. “Reduction in repetitive head impacts from playing football or other activities through additional rule and equipment changes may be associated with reduced mortality.”
The risk of concussions has long been a problem in football on both the professional and youth levels.
In 2018, approximately 5.22 million people in the US played tackle football, according to the Outdoor Foundation.
In high school, there were an estimated 55,007 concussions during the 2005 season.
However, exposure to subconcussive blows is not currently known, which can cause cumulative neurodegenerative damage.
Several clinical studies of high school football players have shown biochemical and neurological changes as well as blood-barrier disruption after subconcussive hits to the head.
The investigators plan to focus future studies on the effects of head impacts on youth, high school, and college football players. They also plan to expand the research into other sports and activities in an effort to make sports safer.
The study, “Association of Professional Football Cumulative Head Impact Index Scores With All-Cause Mortality Among National Football League Players,” was published online in JAMA Network Open.