Bicycle safety helmet legislation and bicycle-related non-fatal injuries in California

The objective of this study was to determine whether the bicycle safety helmet legislation in California, enacted in 1994, was associated with statistically significant reductions in head injuries among bicyclists aged 17 years and under who were subjected to the law. The study used 44,069 patient discharge cases from all public hospitals in California, from 1991 through 2000, and a case-control design to make direct comparisons between those subjected to the law (Youth) and those who were not (Adult) across the pre- and post-legislation periods. An aggregate data analysis approach and a pooled disaggregate data fitting technique using multinomial logit models were applied. The legislation was found to be associated with a reduction of 18.2% (99% confidence interval: 11.5-24.3%) in the proportion of traumatic brain injuries (Head-TBI) among Youth bicyclists. The proportions of other head, face, and neck injuries were not significantly changed across the pre- and post-legislation periods in this age group but there was a corresponding increase of 9% (5-13%) in the proportion of all other injuries. On the other hand, there was no statistically significant change in the proportions of injury outcomes for Adult bicyclists. The youngest riders, aged 0-9 years, had the greatest decrease in the proportion of Head-TBI. The reduction was the same for motor vehicle and non-motor-vehicle-related incidents. The bicycle safety helmet legislation was associated with a decrease in the likelihood of Head-TBI for non-urban residents but not for urbanites, for males but not for females, and for Whites, Asians, and Hispanics, but not Blacks and others.