Hits to center of head are more predictive of concussions for athletes: Study
Rotational acceleration was believed to be the primary concussion risk factor.
Hits to the center of the head are more predictive of concussions than hits that cause the head to rotate, a new study finds.
Previously, it was believed that rotational acceleration -- which occurs when a hit to the head is off-center and causes the head to twist quickly -- was the primary risk factor for concussions.
However, the new research suggests that linear acceleration -- a direct blow to the head's center -- is more predictive. The findings may highlight gaps in knowledge about what kinds of injuries are more likely to lead to concussions.
The study comes on the heels of recent research that has analyzed how many deceased former NFL players may have had chronic traumatic encephalopathy (CTE), a brain disease caused by repeated hits to the head.
For the study, published in the journal the Annals of Biomedical Engineering on Monday, researchers from the U.S. and Australia looked at 203 male and female athletes who suffered about 3,800 impacts.
The team used motion-sensor mouth guards to record the way the impact happened. The impacts were videotaped and assessed by the researchers.
A total of 47 concussions were recorded, and many were caused by injuries to the center of the head rather than rotational head injuries.
Center of the head injuries could be a collision jab between the eyes, a collision to the top of the head or a fall backward with the head hitting the ground.
Since it was believed that rotational injuries could lead to the most serious harm, many American football helmets have been designed with a slippery lining to slow down acceleration of rotation, according to the study.
The researchers tested helmets with a fluid-filled cushion lining that showed a decline in concussive outcomes when hits occurred to the center of the head compared to standard helmets.
Despite center of head hits being more predictive, the findings do not suggest that rotational head injuries are less dangerous or don't cause concussions.
"This study adds important, though still early, evidence to our understanding of concussion biomechanics," Dr. Christine Greiss, medical director at the Center for Brain Injuries at Hackensack Meridian JFK Johnson Rehabilitation Institute in New Jersey told ABC News. "Its findings challenge the long-held assumption that rotational acceleration alone is the primary driver of concussion risk and support a broader assessment that also considers linear acceleration and rotational velocity."
Greiss, who was not involved in the study, said further research is needed to confirm how the findings would translate into clinical practice, but raises points about the need to make sure patients are screened carefully.
"In the past, we felt as providers that this was the least injurious of all mechanisms. But now we know that may not be the case," she added. "Prompt recognition and assessment are essential to avoid delays in treatment and potentially reduce the risk of long-term symptom progression."
The new study comes on the heels of research earlier this year that found three in four former NFL players had CTE at the time of their deaths and about one in four former NFL players had dementia during their lifetime.
That study examined 2,362 deceased former NFL players. Of those, 396 had donated their brains; 1,966 had not.
Among the brain donors, 93.5% had CTE. After accounting for differences in brain donation practices, researchers estimated that 74.5% of the former players had the disease.
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