April 25, 2006
Skull Study Proves Bike Helmets Work
Dropped or hit hard, helmeted skulls didn't crack under pressure, researchers say
Experiments conducted with water-filled human skulls confirm that bike helmets that meet U.S. standards do protect kids from head injury.To come up with the results, the researchers dropped helmeted skulls onto a metal anvil, testing whether the helmets protected against fracture-inducing impact.
While the method may seem startling, the results should please parents everywhere.
"We were able to objectively measure that helmets do provide a benefit, absolutely, beyond question," said study lead author Dr. Chris A. Sloffer, a neurosurgical resident at the University of Illinois College of Medicine, in Peoria.
The findings were expected to be presented Tuesday at the annual meeting of the American Association of Neurological Surgeons in San Francisco.
Sloffer and his co-author, pediatric neurosurgeon Dr. Julian J. Lin, noted that an estimated half a million Americans sought emergency treatment for bicycle-related injuries in 2004. Head injuries accounted for 69,500 of these cases.
In the same year, 600 people died as a result of bicycle accidents, with two-thirds of those deaths due to traumatic brain injuries.
The researchers further pointed out that children 15 and younger are the age pool at greatest risk for bicycle injuries, accounting for 40 percent of related deaths.
In the United States, the most recent national safety standards for bicycle helmets were established by the Consumer Product Safety Commission (CPSC) in 1999. The standards were drafted to ensure that helmets do not block rider vision, do not come off when a rider falls, and offer significant protection upon impact with a hard surface.
Sloffer and Lin assessed these standards by testing four identical, commercially available helmets on four human skulls. The skulls had been filled with water to approximate the weight of a child's head -- about four pounds.
The researchers dropped the skulls -- bare or helmeted -- from various heights onto a metal anvil. Skulls without helmets were dropped from a height of two feet and up until a fracture was observed.
Acceleration monitors fitted onto all the skulls compared degrees of impact deceleration -- the force the head absorbs when it's forced to come to a quick stop.
The researchers found that U.S. standard helmets offered the intended head-injury impact protection in falls originating from as high as three feet off the ground. The tests did not involve drops from heights exceeding three feet, so it's unclear what protection might be offered beyond that level, Sloffer said.
In contrast, un-helmeted skulls experienced impacts approximately four to eight times that of helmeted skulls in the heights tested.
Further tests, designed to simulate accidents involving "crushing situations" -- such as being impacted by a vehicle -- demonstrated that helmeted skulls are able to resist compression at loads as high as 470 pounds. By contrast, un-helmeted skulls fractured under these conditions.
"These tests demonstrated that there is a significant decrease in deceleration -- the force that the head feels when it comes to a quick stop -- if you are wearing a helmet compared to if you are not," said Sloffer.
This benefit should hold up whether a bicyclist simply falls on his or her head, or suffers a crushing impact, the researchers found.
Future study should explore the relationship between the force of impact and the degree and nature of brain injuries, the researchers said. And because helmets used for skateboarding, in-line skating, baseball, and roller hockey are governed by different CPSC standards, the team said their future research will also focus on the relative benefits of these types of equipment.
The findings should give helmet-less bikers pause for thought, Sloffer said.
"To people who are against wearing helmets because of freedom issues or what have you, I can now say that, 'Yes, there is a benefit [to helmets], and I can prove it,' " he said.
Sloffer believes the findings can help improve helmet design, too.
"Helmet designers could always use our methods and take what we've learned, feeding that back into the helmet design stage to make a helmet that's even better and provides even greater protection," he said. "There's no reason why we couldn't design a helmet that is even better."
Dr. Dennis Durbin, a pediatric emergency physician at the Children's Hospital of Philadelphia and a member of the National Committee on Injury and Poison Prevention with the American Academy of Pediatrics, expressed enthusiasm for the findings.
He said the current study backs up earlier lab work conducted in the mid-1990s. That research suggested that bicycle helmets reduced the risk of serious brain injury in an accident by up to 88 percent.
But Durbin cautioned that all the research in the world won't make a difference if riders aren't aware of how best to wear a helmet in the first place.
"They have to fit snugly to the head, low over a forehead," he advised. "A lot of people put it on and flip it back on their head, so if they were to look up, they would not see the brim of the bicycle helmet, and that is not good. People need to be made more aware that there's a proper way to wear a bicycle helmet, if you want to get the maximum benefit out of it," he said.
For more on bike helmet safety, visit Bicycle Helmet Safety Institute.