Objective: To rebut criticism of a previous study of motorcycle helmet-use laws through reanalysis with improved measures of exposure, stratification for regional differences in crash risk, and addressing of total motorcycle-related mortality and the grounds for targeting motorcyclists for helmet-use laws.
Design: Death certificate-based correlational study of motorcycle-related deaths and motorcycle helmet-use laws.
Population studied: United States resident deaths from 1979 through 1986.
Results: Regardless of the denominator used (resident population, motorcycle registrations, or motorcycle crashes), states with full helmet-use laws had consistently lower head injury-associated death rates than states without such laws, even when stratified by region. Total motorcycle-related mortality, however, was similar between law groups. On a registration or crash basis, motorcyclists who died in crashes had a fivefold to sixfold higher risk of head injury than those who died using any other type of motor vehicle.
Conclusion: Full helmet-use laws were consistently associated with lower rates of head injury-associated death. While disagreement remains on the acceptability of the legislative approach, the scientific basis for motorcycle helmet-use laws as a head injury prevention tool appears sound.