This article has a correction
- D L Robinson, senior statistician (email@example.com)1
- University of New England, Armidale, NSW 2351, Australia
- Accepted 9 November 2005
Case-control studies suggest that cyclists who choose to wear helmets have fewer head injuries than non-wearers. Consequently, the BMA recommended that the United Kingdom introduce and enforce bicycle helmet laws.1 However, regular exercise such as cycling is beneficial to health, and non-helmeted commuter cyclists have lower mortality than non-cyclists.2 Helmet laws would be counterproductive if they discouraged cycling and increased car use. Wearing helmets may also encourage cyclists to take more risks, or motorists to take less care when they encounter cyclists.3 Recent epidemiological research highlighted problems adjusting for confounders in observational studies, causing biased, misleading results.4 Thus the best estimate of the benefits of helmet laws is what actually happens when laws are passed.
I reviewed data from all jurisdictions that have introduced legislation and increased use of helmets by at least 40 percentage points within a few months: New Zealand, Nova Scotia (Canada), and the Australian states of Victoria, New South Wales, South Australia, and Western Australia. To avoid confusing reductions in injuries (from safer roads or less cycling) with benefits of helmets, I have focused on percentages of cyclists with head injuries. Head injuries were most commonly classified as admissions to hospital with head wounds, skull or facial fracture, concussion, or other intracranial injury. The data include 10 504 head injuries, and in most cases were available as percentages of all cyclist injuries. Details of data sources and methods are given on bmj.com.
Effects of improving road safety
Road safety initiatives often yield substantial benefits. For example, random breath testing in New South Wales produced an obvious, sustained reduction in deaths. Another campaign, about the same time as the helmet law, …