Falls top the list of how young children injure their heads and assaults and sports are more common causes in teens, according to a new study.

Traumatic brain injury is the leading cause of death and disabilities in children older than one year of age, a previous U.S. study suggests, but few details were known.

Bicycle helmet

For children with head injuries caused by bicycle crashes, 18 per cent wore helmets, according to a new study. (Adam Berry/Getty)

In Wednesday’s New England Journal of Medicine, researchers shed some light on how often head injuries in children and teens resulted in significant brain injuries, based on visits to 25 emergency departments from 2004 to 2006.

For those under age two, falls accounted for 77 per cent of the injuries. For children aged two to 12, falls accounted for 38 per cent of head injuries, Dr. Kimberly Quayle, a professor of pediatrics at Washington University and her co-authors found.

In teenagers, the causes were more varied.

"Head injuries in adolescents most often were caused by assaults, sports activities and motor-vehicle crashes," Quayle said in a release.

Wearing a seat belt or other restraint still resulted in 64 per cent having head injuries. 

For children with head injuries caused by bicycle crashes, 18 per cent wore helmets.

"Our findings may be useful in the development of future injury-prevention measures and age-stratified interventions, such as campaigns to promote the use of bicycle helmets and automobile restraints," the study’s authors concluded.

In the study, children with head injuries were categorized based on severity from normal neurological status to deep coma. Injuries were grouped as mild, moderate or severe based on a common scale that doctors use to assess the mental status of trauma patients.

Of the 43,399 patients in the study, 78 died.

About 98 per cent of the children and teens were considered to have mild head trauma.

Head CT exams were done on 37 per cent of the patients, many arguably unnecessarily, Quayle said.