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Economic disparity in bicycle helmet use by children six years after the introduction of legislation

Macpherson AK, Macarthur C, To TM, Chipman ML, Wright JG, Parkin PC
Injury Prevention, 2006;12:231-235

Original paper

see also: Errors and omissions in Canadian research group's bicycle helmet papers


Summary of paper
(based on authors' abstract)

Objective: To examine bicycle helmet use by children six years after introduction of the Ontario helmet law, and the influence of area level family income on helmet use.
Methods: The East York (Toronto) health district (population 107 822) was divided into income areas (designated as low, mid and high) based on census tract data from Statistics Canada. Child cyclists were observed at 111 preselected sites (schools, parks, residential streets and major intersections) from April to October in the years 1995-97, 1999 and 2001. The frequency of helmet use was determined by year, income area, location and sex. Stratified analysis was used to quantify the relation between income area and helmet use, after controlling for sex and bicycling location.
Results: Bicycle helmet use in the study population area increased from a pre-legislation level of 45% in 1995 to 68% in 1997, then decreased to 46% in 2001. Helmet use increased in all three income areas from 1995 to 1997 and remained above pre-legislation rates in high income areas (85% in 2001). In 2001, six years post-legislation, the proportion of helmeted cyclists in mid and low income areas had returned to pre-legislation levels (50% and 33% respectively). After adjusting for sex and education, children riding in high income areas were significantly more likely to ride helmeted than children in low income areas across all years (relative risk = 3.4, 95% confidence interval, 2.7 to 4.3).
Conclusion: Over the long term, the effectiveness of bicycle helmet legislation varies by income area. Alternative, concurrent or ongoing strategies may be necessary to sustain bicycle helmet use among children in mid and low income areas following legislation.

BHRF Commentary

Cycle use

The authors claim they couldn’t find an association between Ontario’s helmet law and reduced cycling, because cycle use is also affected by weather (1999 was an unusually sunny summer) and random variation. Well-designed surveys try to minimize such variation by observing at the same time of day and day of the week and adjusting for the effect of weather. The authors failed to do this. So it is hardly surprising that no effect could be detected.

Large reductions in cycling were noted in countries where pre- and post-law surveys were conducted in similar weather at the same sites and observation times. Helmet laws were also found to be a major deterrent when cyclists were questioned about barriers to cycling. It is therefore reasonable to conclude that the survey in Ontario was unable to detect an effect of legislation because of poor design and analysis, although a minimally-enforced law (as is the case in Ontario) is likely to be less of a deterrent than laws with substantial enforcement.

Other data presented previously by the first author but not included in this paper shows the variation in percent helmet wearing by location (Macpherson, 2005b):

 
1995
1996
1997
1999
2001
Schools
68.6%
79.7%
80.7%
78.1%
60.1%
Parks
49.1%
76.4%
63.0%
41.0%
39.6%
Major intersections
36.3%
53.2%
56.5%
36.4%
32.2%
Residential streets
36.4%
51.8%
54.0%
40.2%
26.8%

At all four types of location percent helmet wearing was lower in 2001 than pre-legislation in 1995. Taking simple averages of the four location types, percent helmet wearing was 47.6% in 1995 but only 39.7% in 2001 - a fall of 8 percentage points.

However, in this paper the authors say that percent helmet wearing was the same in 2001 as pre-law for low and middle income groups and higher for children from high income families. The only way that could happen is if there was a big decline in cycling by children from high income families (who otherwise still wear helmets) compared to children from low and middle income families (who are more likely to disobey the law). Does the fact that children from high income families feel obliged to wear helmets have anything to do with the fact that fewer of them now cycle?

Vital information on head injury rates not mentioned

The authors state that in Ontario (2001/2002) 104 child cyclists (aged 5-14) were admitted to hospital with head injuries. However, they fail to report the number of non-head injuries, or whether the return to pre-law (or perhaps below pre-law) helmet wearing increased head injury rates.

It is unfortunate that this vital piece of information was not reported. If there was no increase in head injury rates when helmet wearing returned to pre-law levels, there is no merit in adopting new measures to increase helmet use. Efforts spent on other road safety measures could have a much greater impact in reducing injuries.

Some light can be shed on this issue by considering data from another source. For Ontario as a whole, hospitalizations for bicycle-related injuries in children aged 5-19 years declined by 12.5% from 1997/8 to 2001/2, while bicycle-related head injuries for this age group decreased by 26% (CIHI, 2003). Thus head injuries declined at a faster rate than non-head injuries, despite the return to pre-law helmet wearing (at least in East York which had the benefit of helmet and safety programs not carried out elsewhere in Ontario or Canada; unfortunately there is no data for other districts in Ontario). This suggests that earlier research claiming the different trends in head injury rates of legislation and non-legislation provinces were due to increased helmet wearing was probably incorrect and should be withdrawn (Macpherson et al, 2002).

Conclusion

The authors have used the poor design of their surveys to avoid drawing attention to the fact that cycling may have been discouraged in East York, at least for high income children whose helmet wearing did not return to pre-law levels. Similarly they do not mention that head injury rates have continued to decline despite no net increase in helmet wearing over the survey period. Their call for alternative, concurrent or ongoing strategies to increase helmet wearing would be more productively applied to broader measures to encourage cycling and make it safer.

References

CIHI, 2003

Bicycle-Related Injuries Among Ontario Children Declining. Canadian Institute for Health Information March 19 2003.2003.

Macpherson et al, 2002

Macpherson AK, To TM, Macarthur C, Chipman ML, Wright JG, Parkin PC, 2002. Impact of Mandatory Helmet Legislation on Bicycle-Related Head Injuries in Children: A Population-Based Study. Pediatrics 2002; 110(5):e60.

Macpherson, 2005b

Macpherson AK, . An evaluation of the effectiveness of bicycle helmet legislation. University of York, Powerpoint presentation - data underlying slide 37 .

See also