Bicycle helmet legislation for the uptake of helmet use and prevention of head injuries

Background Evidence exists to suggest that bicycle helmets may reduce the risk of head injuries to cyclists, however helmets are not uniformly worn by all bicycle users. Legislation has been enacted in some countries and jurisdictions to mandate helmet use by cyclists, however the issue remains controversial with opponents arguing that helmet laws may inhibit people from bicycle riding and thus from gaining the associated health benefits, or that other countermeasures (e.g. improved road safety) may have been responsible for the observed decline in head injuries. Objectives To assess the effects of bicycle helmet legislation on bicycle‐related head injuries and helmet use, and the occurrence of unintended adverse consequences. Search methods We searched Cochrane Central Register of Controlled Trials (The Cochrane Library 2009, Issue 1); The Cochrane Injuries Group specialised register (searched July 2009), MEDLINE (Ovid SP) (1950 to April 2010), EMBASE (Ovid SP) (1980 to April 2010), CINAHL (EBSCO) (1982 to April 2010), TRANSPORT (Ovid SP) (1988 to September 2009) and other specialist electronic databases. In addition we searched government websites, handsearched selected journals and examined the reference lists of selected publications. Selection criteria We included studies that reported changes in either the number of head injuries, helmet use or bicycle use post‐ versus pre‐legislation. Only studies that included a concurrent control group and which reported on the effect of legislation implemented at either the country, state or province wide level were included. Data collection and analysis Two authors independently extracted data and assessed methodological quality. The data were not appropriate for meta‐analysis, thus the results of the included studies have been reviewed narratively. Main results Six studies, all with a non‐randomised, controlled before and after study design met the inclusion criteria. For each of the studies, bicycle helmet legislation had been enacted for children only. Adults were used as controls in five of the studies, whilst jurisdictions with no helmet legislation were used as controls in the sixth. One study reported on bicycle related mortality while three of the studies reported on changes in head injury rates and three reported on changes in helmet use. There were no included studies reporting change in bicycle use or other adverse consequences of legislation. In three studies, statistically significant decreases in m