MINI CASE 9.2

There have been a number of studies that have found that cycle helmets are effective in reducing head injury to cyclists. By integrating the results of these independent studies (using a statistical procedure known as ‘meta-analysis') Attewell et al. (2001) found that wearing cycle helmets reduced the risk of head injury, facial injury and fatal injury by 60 per cent, 47 per cent and 73 per cent respectively. However, the risk of neck injury was increased by 36 per cent.

In re-examining the Attewell study, Elvik (2011) suggests that some earlier studies had not been included and therefore the analysis had ‘publication' bias, i.e. the researcher attaches more weight to positive outcomes than negative outcomes. Elvik re-analyzed the Attewell data, adjusted for ‘publication' bias and also added post-2001 study data. He concluded that the protective effects attributed to cycle helmets where not as great as Attewell suggests: the risk of head injury was reduced by 42 per cent, risk of facial injury was reduced by only 17 per cent, and the risk of neck injury was increased by 32 per cent. Elvik also makes the comment that although cycle helmets clearly reduce the risk of head injury this risk varies according to the type of helmet used, and suggests that the more common soft shell helmets offer less protection than hard shell helmets.

In New Zealand, where cycle helmets are compulsory, the media reported on Elvik's findings. One newspaper report, although supporting the wearing of helmets because they can reduce the risk of head injuries, highlighted one finding: the wearing of a helmet had negligible effect on the combined risk of head, face or neck injury.

Elvik's findings were also reported in the cycling press prompting debate between the pro and anti-cycle helmet wearers.