Hewson Paul J
Environment Directorate, County Hall, Devon County Council, Topsham Road, Exeter EX2 4QW, UK.
Accid Anal Prev. 2005 Sep;37(5):807-15. doi: 10.1016/j.aap.2005.03.020.
Case control studies suggest that cycle helmets offer their wearers protection from injury in the event of an accident. Nevertheless, encouragement and even compulsion of cycle helmet wearing has been controversial. This paper will re-examine another potential source of evidence for the role of cycle helmets. Administrative datasets are attractive because of their availability, but require careful analysis. The results presented here are obtained from analysing such data with an appropriate form of generalised additive model. Whilst helmet wearing surveys in the UK suggest strongly divergent trends in wearing rates between male and female children, there is little evidence from "Hospital Episode Statistics" to indicate similarly divergent trends in terms of head injury. Conversely, it can be confirmed that head injuries are falling faster among cyclists than pedestrians. Although case control studies suggest cycle helmets are not effective in reducing overall injuries, it is worth noting an increase in the proportion of male child cyclists reported by the police as being killed or seriously injured in road collisions. It might be tempting to use these results to suggest that helmets are not effective in reducing head injury at the population level. Whilst the careful analysis of population level data presented here is clearly important, this paper will discuss the reasons why population and individual level analyses of cycle helmets might be different and consider some of the difficulties in assigning cause and effect with imperfect observational data.
病例对照研究表明，自行车头盔能在事故发生时为佩戴者提供保护，使其免受伤害。然而，鼓励甚至强制佩戴自行车头盔一直存在争议。本文将重新审视自行车头盔作用的另一个潜在证据来源。行政数据集因其可得性而颇具吸引力，但需要仔细分析。此处呈现的结果是通过使用适当形式的广义相加模型分析此类数据而获得的。虽然英国的头盔佩戴情况调查显示，男童和女童的佩戴率趋势差异很大，但“医院事件统计数据”几乎没有证据表明头部受伤情况存在类似的差异趋势。相反，可以确认的是，骑自行车者头部受伤的下降速度比行人更快。尽管病例对照研究表明自行车头盔在减少总体伤害方面并不有效，但值得注意的是，警方报告的在道路碰撞中死亡或受重伤的男童骑自行车者的比例有所增加。可能会有人倾向于利用这些结果表明头盔在总体人群层面上对减少头部伤害无效。虽然此处对总体人群层面数据的仔细分析显然很重要，但本文将讨论自行车头盔在总体人群层面和个体层面分析可能不同的原因，并考虑在使用不完美的观察数据来确定因果关系时遇到的一些困难。
