FRIDAY, Nov. 19 (HealthDay News) -- As more young people ride motorcycles without wearing helmets in the United States, more serious head injuries and long-term disabilities from crashes are creating huge medical costs, two new companion studies show.

In 2006, about 25 percent of all traumatic brain injuries sustained in motorcycle crashes involving 12- to 20-year-olds resulted in long-term disabilities, said study author Harold Weiss. And patients with serious head injuries were at least 10 times more likely to die in the hospital than patients without serious head injuries.

One study looked at the number of head injuries among young motorcyclists and the medical costs; the other looked at the impact of laws requiring helmet use for motorcycle riders, which vary from state to state. Age-specific helmet use laws were instituted in many states after mandatory laws for all ages were abandoned years ago.

"We know from several previous studies that there is a substantial decrease in youth wearing helmets when universal helmet laws are changed to youth-only laws," said Weiss, director of the injury prevention research unit at the Dunedin School of Medicine, New Zealand. He was at the University of Pittsburgh when he conducted the research.

Using hospital discharge data from 38 states from 2005 to 2007, the study found that motorcycle crashes were the reason for 3 percent of all injuries requiring hospitalization among 12- to 20-year-olds in the United States in 2006.

One-third of the 5,662 motorcycle crash victims under age 21 who were hospitalized that year sustained traumatic head injuries, and 91 died.

About half of those injured or killed were between the ages of 18 and 20 and 90 percent were boys, the study found.

The findings, published online Nov. 15 in Pediatrics, also showed that head injuries led to longer hospital stays and higher medical costs than other types of motorcycle accident-related injuries.

For instance, motorcycle crash-related hospital charges were estimated at almost $249 million dollars, with $58 million due to head injuries in 2006, the study on injuries and costs found. More than a third of the costs were not covered by insurance. Citing other research, the study noted that motorcycle injuries, deaths and medical costs are rising.

Previous research has shown that helmet use reduces head injuries by 69 percent, and deaths from head injuries by 42 percent, according to the helmet laws' study.

Enforcement of helmet laws falls off when mandatory universal laws are rolled back because it's difficult to determine a rider's age prior to a traffic stop, and police begin to see it as less of a priority, according to research cited in the study.

When enforcement declines, young people stop wearing helmets, resulting in increasing numbers of head injuries, the study noted. In fact, in states with a law requiring only youth under 21 to wear helmets, the study found, the rate of serious motorcycle-related traumatic brain injury among youth was 38 percent higher than in states with universal helmet laws.

The hospital data did not distinguish among motorcycles, mopeds and motorized scooters, the authors said.

Only 20 states and Washington, D.C., have mandatory universal helmet use laws, and several of those are considering rolling them back in favor of age-specific helmet laws, either for those under 21 or under 18. The study concluded, however, that helmet laws limited to young people are ineffective at protecting them.

Thirty states repealed mandatory helmet use laws after 1976, when Congress prevented the Department of Transportation from withholding highway safety funds from states without universal helmet use laws, the study found. Sanctions were reinstated and again repealed in the 1990s after lobbying by groups opposed to mandatory helmet use laws, said Weiss.

Arthur Goodwin, senior research associate at the Highway Safety Research Center at the University of North Carolina, in Chapel Hill, said a mandatory universal helmet law is the only measure proven to help reduce motorcycle injuries and fatalities.

"Only one countermeasure is considered proven to be effective at reducing crashes and injuries: state motorcycle helmet use laws. A review of 46 studies suggested motorcycle rider fatality rates were 20 to 40 percent lower in states with universal helmet laws," said Goodwin. "A universal helmet law is without doubt the single most important thing any state can do to reduce injuries and fatalities among motorcycle riders."

For all ages, the National Highway Traffic Safety Administration estimates that $13.2 billion was saved from 1984 through 1999 because of the use of motorcycle helmets. An additional $11.1 billion would have been saved if all motorcyclists had worn helmets.

Mandatory helmet use laws for all is the only way to protect young people from serious head injury and death from motorcycle crashes, the researchers concluded.

More information

For more on motor vehicle safety, see the U.S. National Library of Medicine.