The design of football helmets can effect concussion risk, finds a new study by some of the nation's top concussion researchers.
The study provides what the authors say is good clinical evidence that helmet design can lower the risk of concussion, not in a laboratory, but in games and practices, by showing that a helmet model introduced in 2000 provides better protection against concussion than an older helmet employing 20-year-old design technology.
But it leaves unanswered the practical question faced by football parents, coaches, and administrators as to whether a difference in concussion risk reduction exists between new helmet models incorporating such new design features, and does nothing to change the prevailing view that no helmet has yet been designed which can prevent all concussions.
New: better than old?
Analyzing helmet sensor data on 1.2 million head impacts sustained by more than 1,800 football players on eight collegiate teams, along with the number of diagnosed concussions they suffered, over a six-year period between 2005 and 2010, researchers identified a 53.9% reduction of concussion risk associated with a newer model of Riddell helmet, the Revolution (helmet on left in photograph), compared to an older model Riddell helmet, the VSR4 (helmet on the right). The Technical note was published online in the Journal of Neurosurgery (Rowson S, Duma SM, et al 2014).
Not only did players wearing the VSR4 helmets have a per-impact concussion rate more than twice as high as the rate for those wearing the Revolution helmet (8.37 concussions per 100,000 head impacts versus 3.86 concussions per 100,000 head impacts), but they also experienced higher acceleration impacts more frequently, regardless of the position they played.
The study's authors, who included such leading concussion researchers as Kevin Guskiewicz of the University of North Carolina and Steven Broglio of the University of Michigan, attributed the results to the Revolution helmet doing a better job of attenuating impact energy transferred to the head, findings consistent with drop tests which showed that the Revolution was better than the VSR4 at reducing linear and rotational acceleration, the forces that cause concussion.
"From a biomechanical standpoint, the difference in concussion risk between helmets is logical," wrote study co-lead author, Stefan Duma, head of the Virginia Tech-Wake Forest School of Biomedical Engineering.
Because a "helmet modulates the energy transfer to the head during impact, which dictates the accelerations that the head will experience, helmets that do a better job of lowering head acceleration reduce concussion risk," he said.
Corrected methodological flaws
While laboratory studies have shown that helmets reduce impact forces, few have evaluated the effectiveness of different helmet designs in reducing concussions in practices and games.
A 2006 study of 2000 high school players (Collins M, Lovell MR, et al 2006) reported that the Riddell Revolution reduced the risk of concussion by 31% compared to other helmets, but has been widely criticized as methodologically flawed for failing to account for impact exposure and the age of the non-Revolution helmet, and as marred by conflicts of interest because it was funded by Riddell.
Data reported by Duma and his Virginia Tech-Wake Forest colleague, Steven Rowson, in a 2012 letter in the Annals of Biomechanical Engineering (Rowson S, Duma SM. 2014) analyzed 9 years of head impact data collected from 308 players. It reported that the Revolution reduced the risk of concussion by 85% compared to the VSR4 helmet. The current study, said Duma, was designed to address the limitations of the 2006 Collins study, expand on the 2012 results with a larger sample size, and control as much as possible for other variables.
Because each player was provided with a new helmet of the two models under investigation, helmet age did not vary. Each of the eight teams had a team physician and athletic trainers to monitor and evaluate players during games and practices, and the same team doctor made each concussion diagnosis throughout the study period.
"Most importantly," said Duma, by controlling for the number of head impacts each player experienced, which previous studies have shown varies by player and position, researchers were able to make an apples-to-apples comparison based on better data for addressing the question of whether helmet design can influence concussion incidence than the total number of players or athletic-exposures (e.g. number of games and practices).
The data "illustrates that differences in the ability to reduce concussion risk exist between helmet models in football," the authors concluded.
Our results are grounded on "very sound science," Duma asserted, and provide "solid clinical evidence" that helmet design, while it may never prevent all concussions from occurring in football, can reduce the incidence of this injury. [For the full text of Lindsay Barton's email interview with Professor Duma, click here] Micky Collins, Director of the Sports Medicine Concussion Program at the University of Pittsburgh Medical Center, and author of numerous peer-reviewed concussion studies, including the 2006 helmet study, was not surprised by the Rowson study's findings. That it is now the third study reporting that helmet design can affect concussion risk, he said, made him a "little more confident" and "hopeful" that helmet technology is "going in the right direction."
"Scientific research is a process," Collins said, and he was glad to see the Rowson study "building on his research."Support for STAR helmet ratings
Interestingly, the difference in concussion risk between the two helmets matched almost exactly the estimated difference in concussion risk between the two helmets calculated by the STAR helmet rating system, a test of helmets in a laboratory environment developed by Duma and Rowson, which is designed to measure their effectiveness in reducing the forces that cause concussion. The data obtained from that testing suggested that the Revolution, a 4-STAR helmet introduced in 2000, would result in a 54% reduction in risk of concussion compared to the VSR4, a 1-star helmet employing 20-year-old technology, which was still being worn by as many as 38% of professional players as recently as 2011.\
"We would never have guessed the risk reduction would have matched so closely," said Duma. "We think that this is excellent validation" of the STAR system, and, in our opinion makes the overall STAR ratings very useful."
[For an updated article on the 2014 STAR ratings, click here].
