Unadjusted analyses found that the frequency of cervical spine injury was significantly higher among nonhelmeted riders compared with those who wore helmets (5.4% versus 3.5%, P=0.001), according to Joseph G. Crompton, MD, of the University of California Los Angeles, and colleagues.
In addition, an adjusted analysis revealed that wearing a helmet was associated with a 22% reduction in the odds of injury to the cervical spine (OR 0.78, 95% CI 0.68 to 0.88), the researchers reported online in the Journal of the American College of Surgery.
"Forty years ago, nearly all states required helmets for motorcyclists of any age in the U.S.," Crompton and colleagues observed. Today, however, mandatory helmet laws are on the books in only 20 states, despite a striking rise in motorcycle accidents and fatalities.
Opponents of mandatory helmet laws argue that their use increases the likelihood of cervical spine injuries because the weight of the helmet causes an increase in the torque on the neck upon collision.
To determine if this was the case, the researchers analyzed data from the National Trauma Data Bank for 40,890 motorcycle accidents.
Most of the injured were white men whose mean age was 38 years.
Those not wearing helmets fared worse on a number of outcomes:
- Severe head injury, 18.9% versus 8.5% (P<0.001)
- Shock, 5.8% versus 4.8% (P<0.001)
- Mean injury severity score, 14.7 versus 13.4 (P<0.001)
- Crude mortality, 6.2% versus 3.5% (P<0.001)
The odds of traumatic brain injury fell by 65% (OR 0.35, 95% CI 0.33 to 0.38) among riders wearing helmets, and the odds of death decreased by 37% (OR 0.63, 95% CI 0.55 to 0.73), the researchers found.
"This analysis of the largest trauma database ever assembled demonstrates that injured motorcycle riders are significantly less likely to suffer from a cervical spine injury when wearing a helmet compared with nonhelmeted riders, effectively debunking the myth that motorcycle helmets are associated with higher risk of cervical spine injury after a crash," Crompton's group stated.
The findings are particularly meaningful in light of the increase in these accidents and injuries worldwide in recent years, they noted.
An earlier study that suggested an increase in cervical spine injuries has been criticized by the National Highway Traffic Safety Administration, among others, as being statistically flawed, but the study's effect on helmet use has been "remarkable," they acknowledged.
Previous studies have also been limited to smaller numbers and by lack of adjustment for confounders.
Limitations to the present study include voluntary submission of data to the trauma databank and potential selection bias, lack of data on precise causes of death, and absence of information on accidents that did not result in hospitalization for various reasons, such as because the injuries were minor or the patients died at the scene.
The researchers also were unable to adjust for certain crash-related factors, including vehicle speed, the presence of other vehicles, and type of helmet worn.
"These findings have implications for legislative policy, particularly when research is evaluated during policy debates regarding whether to repeal or implement state mandatory helmet laws," Crompton and colleagues concluded.
The authors declared that they had nothing to disclose.
- Reviewed by Dori F. Zaleznik, MD Associate Clinical Professor of Medicine, Harvard Medical School, Boston and Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner
Journal of the American College of SurgerySource Reference: Crompton J, et al "Motorcycle helmets associated with lower risk of cervical spine injury: debunking the myth" J Am Coll Surg 2011; DOI: 10.1016/j.jamcollsurg.2010.09.032.