Poor and minority children are less likely to be wearing bike helmets when they crash than kids who are white or more affluent, a U.S. study suggests.

Researchers reviewed trauma records for 7,678 bike accidents involving kids under 16 and found just 22 percent of them wore helmets at all.

Riding without a helmet was more common among kids insured by Medicaid, the government health insurance program for the poor, and less typical among children covered by private insurance, often provided by employers. Skipping the helmet was also more likely among black and minority children.

“Our findings are unfortunate but not surprising,” said lead study author Dr. Obinna Adibe, a researcher in pediatric surgery at Duke University Medical Center in Durham, North Carolina. “Head injuries are the most lethal type of injury in these children, and one of the most common.”

In the U.S., more than 3 million people a year are treated in emergency departments for cycling injuries, and more than 300 children die from these crashes, Obinna and colleagues write in the journal Surgery.

The majority of cycling deaths are related to traumatic head injuries, which can be minimized or prevented by helmets, the researchers note.

They reviewed accident records from the National Trauma Database during the years 2007, 2010 and 2011 to see what differentiated children who wore helmets from kids who didn’t.

Half of the children in the study were at least 11 years old, and children who rode without helmets were slightly older.

Black children were 62 percent less likely to be wearing a helmet at the time of their accident than white children.

Kids insured by Medicaid had 67 percent lower odds of helmet use than children with private coverage, suggesting a disparity based on income.

Children injured in accidents in the Midwest and the Southern regions of the U.S. were also less likely to be wearing helmets than kids in the Northeast, the study found.

One shortcoming of the study is that it only looked at children injured seriously enough to require a hospital visit, which may have led to a sample of children who are more reckless riders and less likely to wear helmets, Adibe said by email.

“Overall helmet use rates would be somewhat higher because a non-helmeted rider is more likely to be injured,” said Dr. Greg Parkinson a pediatrician and injury prevention specialist in Falmouth, Massachusetts.

Disparities in helmet use based on race and income aren’t surprising because inequality persists across many other types of childhood injury, Parkinson, who wasn’t involved in the study, said by email.

Bike helmet giveaways have effectively reduced injuries in cities including Seattle, New York and Boston, Adibe said. These programs, as well as state laws mandating helmet use, can help overcome the cost barrier that keeps some parents from getting helmets for their children.

“In states without laws mandating helmet use, parents may see purchasing a helmet as an unnecessary expense,” Adibe said. “As far as the racial difference, this is partially socioeconomic, partially institutional bias in overall education of black children in our country.”

Parents should also set a good example for children by wearing helmets themselves, Parkinson added.

“Bike helmets save lives and prevent serious brain injuries,” Parkinson said. “It is essential for children to wear helmets, and equally essential for parents to protect themselves and model good behavior for their children to emulate.”