Arguments against helmet legislation are flawed

Abstract

What do the data show? Robinson suggests that the percentage of bicycle related injuries that are head injuries seems to be declining and that this decline started before the enactment of the law. However, her figures also show that helmet laws are successful in increasing helmet use and seem to be associated with a decrease in the percentage of head injuries. The effect of helmet use is most evident in her fig 2, where the increase in the percentage of cyclists wearing helmets corresponds with a decrease in the percentage of head injuries. The correlation coefficient for the percentage helmet use and percentage head injury is −0.8 for children and −0.9 for adults. The corresponding r2 of 0.64 for children and 0.81 for adults suggests that much of the variation in the percentage of head injuries is explained by helmet use. Thus, as the proportion of helmeted cyclists increases, the proportion of bicycle related head injuries decreases. Beware of confounders Credit: ED PRITCHARD/STONE/GETTY IMAGES This relation is also apparent in the New South Wales data on bmj.com. Bicycle related head injuries in children declined by 1.2% and 0.8% in the two years before the enactment of the helmet law and then by 4.3% immediately after the law. The decline of 1.6% in the following year was still greater than in the two years before the law.