Objective. Childhood bicycle-related head injuries can be prevented through the use of helmets. Although helmet legislation has proved to be a successful strategy for the adoption of helmets, its effect on the rates of head injury is uncertain. In Canada, 4 provinces have such legislation. The objective of this study was to measure the impact of helmet legislation on bicycle-related head injuries in Canadian children.
Methods. Routinely collected data from the Canadian Institute for Health Information identified all Canadian children (5–19 years) who were hospitalized for bicycling-related injuries from 1994–1998. Children were categorized as head or other injury on the basis of International Classification of Diseases, Ninth Revision, codes. Rates of head injuries and other injuries were compared over time in provinces that adopted legislation and those that did not.
Results. Of the 9650 children who were hospitalized because of a bicycle-related injury, 3426 sustained injuries to the head and face and the remaining 6224 had other injuries. The bicycle-related head injury rate declined significantly (45% reduction) in provinces where legislation had been adopted compared with provinces and territories that did not adopt legislation (27% reduction).
Conclusion. This country-wide study compared rates of head injury in regions with and without mandatory helmet legislation. Comparing head injuries with other non-head-injured children controlled for potential differences in children’s cycling habits. The strong protective association between helmet legislation and head injuries supports the adoption of helmet legislation as an effective tool in the prevention of childhood bicycle-related head injuries.
Individual graphs of the two Canadian provinces representing 89% of injuries to child cyclists in legislation provinces1 are very revealing. For British Columbia (BC), the largest single-year fall (7.4 percentage points, from 39.9% to 32.5%) was from 94/95 to 95/96. This could not have been caused by legislation commencing in September 1996 (Fig. 1). A year before legislation (95/96), %HI was 2.7% less than no-law provinces; a year after legislation (97/98), it was 2.5% less. Far from reducing %HI, the effect of legislation in BC relative to no-law provinces was therefore a small, but non-significant increase of 0.2%.
In Ontario, legislation commenced in October 1995.1 Helmet wearing rates and numbers of cyclists were recorded in Toronto, Ontario's largest city. Only numbers of cyclists counted were reported,5 not the changes in helmet wearing with the law, which was apparently not enforced.6 Most cycling in the 95/96 fiscal year would have taken place before legislation, because freezing Ontario winters are not particularly conducive to cycling. Thus the fall from 94/95 to 95/96 was probably not due to legislation, but an expression of the same trend as BC, noted above to be unrelated to the law. The main increase in helmet wearing in Ontario, and hence and main effect of the helmet law, should have been evident in 96/97 data, but this is not apparent from Fig 1. Unless there is reason to believe that legislation in October 1995 increased wearing rates in 97/98 significantly above those in 96/97, it seem implausible that the largest fall in %HI (from 33.9% in 96/97 to 28.5% in 97/98) was actually due to helmet legislation.
Fig. 1 shows that, despite the effect of legislation and slightly fewer bike/motor vehicle crashes in helmet-law provinces1 (which should result in marginally lower %HI), post-law %HI in Ontario and BC was not significantly different to no-law provinces. The largest differences in %HI were before, not after, the laws. This strongly suggests that trends, rather than the helmet legislation, may have been responsible for the changes over time.
Macpherson et al. claimed that the Canadian data, most of which is shown in Fig. 1, show a "strong protective association between helmet legislation and head injuries".1 The fact that the largest changes in head injury rates happened either before (in BC), or more than a year after (Ontario) the start of legislation, and that post law %HI in legislation provinces was not significantly different to %HI in provinces with no legislation, suggests that this conclusion is highly questionable.