Subjects, methods, and results

We studied all children admitted to hospital and about 75% of children attending emergency departments. Data on admissions were checked against the health department's patient register and deaths against necropsy files. Missing data were obtained by retrospective analysis of case notes. Demographic data are given in the accompanying paper.3

From 1 July 1985 to 30 June 1991, 46 523 children under 14 years of age attended the emergency departments and 7156 were admitted to hospital. Head injuries not due to bicycle accidents fell significantly after age and sex were adjusted for (P<0.001) but no significant trend occurred in annual attendance or admission rates for all injuries. Bicycle related injury was the most common injury category, resulting in 3438 attendances, 658 admissions, five deaths, and 283 head injuries. Bicycle related injuries associated with motor vehicle collision were responsible for 292 attendances, 121 admissions, four deaths, and 73 head injuries. The rate of head injury from bicycle accidents fell from 47.34/100 000 (95% confidence interval, 36.30 to 60.72) in 1985 to 18.32/100 000 (11.76 to 27.24) in 1991 (P<0.001). Admissions to hospital with bicycle related injuries other than to the head were unchanged (P>0.6) (figure).

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Trends in bicycle related head injuries and injuries other than head head injuries, and trends in head injuries from all other causes, July 1985 to June 1991

Comment

Collision with a motor vehicle caused only 8.5% of bicycle injuries and 25.8% of bicycle related head injuries. Because helmets are designed to protect the head in accidents when other vehicles are not involved, which is most accidents, the case for wearing helmets is sound.

In 1986 about 2.5% of primary school children wore helmets.4 This had risen to 59% in June 1991, when compulsory helmet wearing was introduced.5 The decrease in bicycle related head injuries started before helmets became widely used and occurred against a background of unchanged admission rates for other bicycle related injuries and a decrease in head injuries from other causes. This suggests that the decrease is not due to decreased exposure of child bicyclists to injury.

Our findings indicate that the reason for the decrease in bicycle related head injuries is more complex than just increased wearing of helmets. Nevertheless, the protective effect of helmets is supported by the large drop in head injuries in the 12 months before legislation, when public debate ensured high levels of awareness and helmet wearing.